diff --git a/src/browser/ReactDOM.js b/src/browser/ReactDOM.js
index 3bc9c5c1027..d4b1303b444 100644
--- a/src/browser/ReactDOM.js
+++ b/src/browser/ReactDOM.js
@@ -14,7 +14,6 @@
 
 var ReactElement = require('ReactElement');
 var ReactElementValidator = require('ReactElementValidator');
-var ReactLegacyElement = require('ReactLegacyElement');
 
 var mapObject = require('mapObject');
 
@@ -26,13 +25,9 @@ var mapObject = require('mapObject');
  */
 function createDOMFactory(tag) {
   if (__DEV__) {
-    return ReactLegacyElement.markNonLegacyFactory(
-      ReactElementValidator.createFactory(tag)
-    );
+    return ReactElementValidator.createFactory(tag);
   }
-  return ReactLegacyElement.markNonLegacyFactory(
-    ReactElement.createFactory(tag)
-  );
+  return ReactElement.createFactory(tag);
 }
 
 /**
diff --git a/src/browser/__tests__/ReactDOM-test.js b/src/browser/__tests__/ReactDOM-test.js
index c47ef01f69b..b839089d2b8 100644
--- a/src/browser/__tests__/ReactDOM-test.js
+++ b/src/browser/__tests__/ReactDOM-test.js
@@ -114,24 +114,4 @@ describe('ReactDOM', function() {
     expect(element.type).toBe('div');
     expect(console.warn.argsForCall.length).toBe(0);
   });
-
-  it('warns but allow dom factories to be used in createFactory', function() {
-    spyOn(console, 'warn');
-    var factory = React.createFactory(React.DOM.div);
-    expect(factory().type).toBe('div');
-    expect(console.warn.argsForCall.length).toBe(1);
-    expect(console.warn.argsForCall[0][0]).toContain(
-      'Do not pass React.DOM.div'
-    );
-  });
-
-  it('warns but allow dom factories to be used in createElement', function() {
-    spyOn(console, 'warn');
-    var element = React.createElement(React.DOM.div);
-    expect(element.type).toBe('div');
-    expect(console.warn.argsForCall.length).toBe(1);
-    expect(console.warn.argsForCall[0][0]).toContain(
-      'Do not pass React.DOM.div'
-    );
-  });
 });
diff --git a/src/browser/ui/React.js b/src/browser/ui/React.js
index 83d15f84d77..19de5a77ea9 100644
--- a/src/browser/ui/React.js
+++ b/src/browser/ui/React.js
@@ -24,7 +24,6 @@ var ReactDOM = require('ReactDOM');
 var ReactDOMComponent = require('ReactDOMComponent');
 var ReactDefaultInjection = require('ReactDefaultInjection');
 var ReactInstanceHandles = require('ReactInstanceHandles');
-var ReactLegacyElement = require('ReactLegacyElement');
 var ReactMount = require('ReactMount');
 var ReactMultiChild = require('ReactMultiChild');
 var ReactPerf = require('ReactPerf');
@@ -46,14 +45,6 @@ if (__DEV__) {
   createFactory = ReactElementValidator.createFactory;
 }
 
-// TODO: Drop legacy elements once classes no longer export these factories
-createElement = ReactLegacyElement.wrapCreateElement(
-  createElement
-);
-createFactory = ReactLegacyElement.wrapCreateFactory(
-  createFactory
-);
-
 var render = ReactPerf.measure('React', 'render', ReactMount.render);
 
 var React = {
@@ -77,7 +68,6 @@ var React = {
   renderToString: ReactServerRendering.renderToString,
   renderToStaticMarkup: ReactServerRendering.renderToStaticMarkup,
   unmountComponentAtNode: ReactMount.unmountComponentAtNode,
-  isValidClass: ReactLegacyElement.isValidClass,
   isValidElement: ReactElement.isValidElement,
   withContext: ReactContext.withContext,
 
diff --git a/src/browser/ui/ReactMount.js b/src/browser/ui/ReactMount.js
index 57a20710ff3..642fe67e5e4 100644
--- a/src/browser/ui/ReactMount.js
+++ b/src/browser/ui/ReactMount.js
@@ -15,7 +15,6 @@ var DOMProperty = require('DOMProperty');
 var ReactBrowserEventEmitter = require('ReactBrowserEventEmitter');
 var ReactCurrentOwner = require('ReactCurrentOwner');
 var ReactElement = require('ReactElement');
-var ReactLegacyElement = require('ReactLegacyElement');
 var ReactInstanceHandles = require('ReactInstanceHandles');
 var ReactPerf = require('ReactPerf');
 
@@ -27,10 +26,6 @@ var invariant = require('invariant');
 var shouldUpdateReactComponent = require('shouldUpdateReactComponent');
 var warning = require('warning');
 
-var createElement = ReactLegacyElement.wrapCreateElement(
-  ReactElement.createElement
-);
-
 var SEPARATOR = ReactInstanceHandles.SEPARATOR;
 
 var ATTR_NAME = DOMProperty.ID_ATTRIBUTE_NAME;
@@ -342,7 +337,7 @@ var ReactMount = {
         typeof nextElement === 'string' ?
           ' Instead of passing an element string, make sure to instantiate ' +
           'it by passing it to React.createElement.' :
-        ReactLegacyElement.isValidFactory(nextElement) ?
+        typeof nextElement === 'function' ?
           ' Instead of passing a component class, make sure to instantiate ' +
           'it by passing it to React.createElement.' :
         // Check if it quacks like a element
@@ -394,7 +389,7 @@ var ReactMount = {
    * @return {ReactComponent} Component instance rendered in `container`.
    */
   constructAndRenderComponent: function(constructor, props, container) {
-    var element = createElement(constructor, props);
+    var element = ReactElement.createElement(constructor, props);
     return ReactMount.render(element, container);
   },
 
diff --git a/src/browser/ui/dom/components/ReactDOMButton.js b/src/browser/ui/dom/components/ReactDOMButton.js
index ed23b00289c..a5fd34caf6d 100644
--- a/src/browser/ui/dom/components/ReactDOMButton.js
+++ b/src/browser/ui/dom/components/ReactDOMButton.js
@@ -15,12 +15,10 @@ var AutoFocusMixin = require('AutoFocusMixin');
 var ReactBrowserComponentMixin = require('ReactBrowserComponentMixin');
 var ReactClass = require('ReactClass');
 var ReactElement = require('ReactElement');
-var ReactDOM = require('ReactDOM');
 
 var keyMirror = require('keyMirror');
 
-// Store a reference to the <button> `ReactDOMComponent`. TODO: use string
-var button = ReactElement.createFactory(ReactDOM.button.type);
+var button = ReactElement.createFactory('button');
 
 var mouseListenerNames = keyMirror({
   onClick: true,
diff --git a/src/browser/ui/dom/components/ReactDOMForm.js b/src/browser/ui/dom/components/ReactDOMForm.js
index 73dcb240795..8af4a2e7b10 100644
--- a/src/browser/ui/dom/components/ReactDOMForm.js
+++ b/src/browser/ui/dom/components/ReactDOMForm.js
@@ -16,10 +16,8 @@ var LocalEventTrapMixin = require('LocalEventTrapMixin');
 var ReactBrowserComponentMixin = require('ReactBrowserComponentMixin');
 var ReactClass = require('ReactClass');
 var ReactElement = require('ReactElement');
-var ReactDOM = require('ReactDOM');
 
-// Store a reference to the <form> `ReactDOMComponent`. TODO: use string
-var form = ReactElement.createFactory(ReactDOM.form.type);
+var form = ReactElement.createFactory('form');
 
 /**
  * Since onSubmit doesn't bubble OR capture on the top level in IE8, we need
diff --git a/src/browser/ui/dom/components/ReactDOMImg.js b/src/browser/ui/dom/components/ReactDOMImg.js
index 29c767515ff..5a0495f107d 100644
--- a/src/browser/ui/dom/components/ReactDOMImg.js
+++ b/src/browser/ui/dom/components/ReactDOMImg.js
@@ -16,10 +16,8 @@ var LocalEventTrapMixin = require('LocalEventTrapMixin');
 var ReactBrowserComponentMixin = require('ReactBrowserComponentMixin');
 var ReactClass = require('ReactClass');
 var ReactElement = require('ReactElement');
-var ReactDOM = require('ReactDOM');
 
-// Store a reference to the <img> `ReactDOMComponent`. TODO: use string
-var img = ReactElement.createFactory(ReactDOM.img.type);
+var img = ReactElement.createFactory('img');
 
 /**
  * Since onLoad doesn't bubble OR capture on the top level in IE8, we need to
diff --git a/src/browser/ui/dom/components/ReactDOMInput.js b/src/browser/ui/dom/components/ReactDOMInput.js
index 2e7c2a94c11..cf3758e55a3 100644
--- a/src/browser/ui/dom/components/ReactDOMInput.js
+++ b/src/browser/ui/dom/components/ReactDOMInput.js
@@ -17,15 +17,13 @@ var LinkedValueUtils = require('LinkedValueUtils');
 var ReactBrowserComponentMixin = require('ReactBrowserComponentMixin');
 var ReactClass = require('ReactClass');
 var ReactElement = require('ReactElement');
-var ReactDOM = require('ReactDOM');
 var ReactMount = require('ReactMount');
 var ReactUpdates = require('ReactUpdates');
 
 var assign = require('Object.assign');
 var invariant = require('invariant');
 
-// Store a reference to the <input> `ReactDOMComponent`. TODO: use string
-var input = ReactElement.createFactory(ReactDOM.input.type);
+var input = ReactElement.createFactory('input');
 
 var instancesByReactID = {};
 
diff --git a/src/browser/ui/dom/components/ReactDOMOption.js b/src/browser/ui/dom/components/ReactDOMOption.js
index d87606e305f..4faa788fb4d 100644
--- a/src/browser/ui/dom/components/ReactDOMOption.js
+++ b/src/browser/ui/dom/components/ReactDOMOption.js
@@ -14,12 +14,10 @@
 var ReactBrowserComponentMixin = require('ReactBrowserComponentMixin');
 var ReactClass = require('ReactClass');
 var ReactElement = require('ReactElement');
-var ReactDOM = require('ReactDOM');
 
 var warning = require('warning');
 
-// Store a reference to the <option> `ReactDOMComponent`. TODO: use string
-var option = ReactElement.createFactory(ReactDOM.option.type);
+var option = ReactElement.createFactory('option');
 
 /**
  * Implements an <option> native component that warns when `selected` is set.
diff --git a/src/browser/ui/dom/components/ReactDOMSelect.js b/src/browser/ui/dom/components/ReactDOMSelect.js
index 62df8a2adba..0b071400b5e 100644
--- a/src/browser/ui/dom/components/ReactDOMSelect.js
+++ b/src/browser/ui/dom/components/ReactDOMSelect.js
@@ -16,13 +16,11 @@ var LinkedValueUtils = require('LinkedValueUtils');
 var ReactBrowserComponentMixin = require('ReactBrowserComponentMixin');
 var ReactClass = require('ReactClass');
 var ReactElement = require('ReactElement');
-var ReactDOM = require('ReactDOM');
 var ReactUpdates = require('ReactUpdates');
 
 var assign = require('Object.assign');
 
-// Store a reference to the <select> `ReactDOMComponent`. TODO: use string
-var select = ReactElement.createFactory(ReactDOM.select.type);
+var select = ReactElement.createFactory('select');
 
 function updateWithPendingValueIfMounted() {
   /*jshint validthis:true */
diff --git a/src/browser/ui/dom/components/ReactDOMTextarea.js b/src/browser/ui/dom/components/ReactDOMTextarea.js
index 7fb6d6c5a19..765d0236520 100644
--- a/src/browser/ui/dom/components/ReactDOMTextarea.js
+++ b/src/browser/ui/dom/components/ReactDOMTextarea.js
@@ -17,7 +17,6 @@ var LinkedValueUtils = require('LinkedValueUtils');
 var ReactBrowserComponentMixin = require('ReactBrowserComponentMixin');
 var ReactClass = require('ReactClass');
 var ReactElement = require('ReactElement');
-var ReactDOM = require('ReactDOM');
 var ReactUpdates = require('ReactUpdates');
 
 var assign = require('Object.assign');
@@ -25,8 +24,7 @@ var invariant = require('invariant');
 
 var warning = require('warning');
 
-// Store a reference to the <textarea> `ReactDOMComponent`. TODO: use string
-var textarea = ReactElement.createFactory(ReactDOM.textarea.type);
+var textarea = ReactElement.createFactory('textarea');
 
 function forceUpdateIfMounted() {
   /*jshint validthis:true */
diff --git a/src/class/ReactClass.js b/src/class/ReactClass.js
index baeaf87d7ff..13ed707fb5e 100644
--- a/src/class/ReactClass.js
+++ b/src/class/ReactClass.js
@@ -13,8 +13,6 @@
 
 var ReactCompositeComponent = require('ReactCompositeComponent');
 var ReactElement = require('ReactElement');
-var ReactElementValidator = require('ReactElementValidator');
-var ReactLegacyElement = require('ReactLegacyElement');
 var ReactPropTypeLocations = require('ReactPropTypeLocations');
 var ReactPropTypeLocationNames = require('ReactPropTypeLocationNames');
 
@@ -679,14 +677,10 @@ var ReactClass = {
       }
     }
 
-    if (__DEV__) {
-      return ReactLegacyElement.wrapFactory(
-        ReactElementValidator.createFactory(Constructor)
-      );
-    }
-    return ReactLegacyElement.wrapFactory(
-      ReactElement.createFactory(Constructor)
-    );
+    // Legacy hook TODO: Warn if this is accessed
+    Constructor.type = Constructor;
+
+    return Constructor;
   },
 
   injection: {
diff --git a/src/core/ReactCompositeComponent.js b/src/core/ReactCompositeComponent.js
index ec56273bcba..0c1f187e144 100644
--- a/src/core/ReactCompositeComponent.js
+++ b/src/core/ReactCompositeComponent.js
@@ -171,6 +171,17 @@ var ReactCompositeComponentMixin = {
       this.props = this._processProps(this.props);
 
       this.state = this.getInitialState ? this.getInitialState() : null;
+
+      if (__DEV__) {
+        // We allow auto-mocks to proceed as if they're returning null.
+        if (typeof this.state === 'undefined' &&
+            this.getInitialState && this.getInitialState._isMockFunction) {
+          // This is probably bad practice. Consider warning here and
+          // deprecating this convenience.
+          this.state = null;
+        }
+      }
+
       invariant(
         typeof this.state === 'object' && !Array.isArray(this.state),
         '%s.getInitialState(): must return an object or null',
@@ -675,6 +686,15 @@ var ReactCompositeComponentMixin = {
       ReactCurrentOwner.current = this;
       try {
         renderedComponent = this.render();
+        if (__DEV__) {
+          // We allow auto-mocks to proceed as if they're returning null.
+          if (typeof renderedComponent === 'undefined' &&
+              this.render._isMockFunction) {
+            // This is probably bad practice. Consider warning here and
+            // deprecating this convenience.
+            renderedComponent = null;
+          }
+        }
         if (renderedComponent === null || renderedComponent === false) {
           renderedComponent = ReactEmptyComponent.getEmptyComponent();
           ReactEmptyComponent.registerNullComponentID(this._rootNodeID);
@@ -781,4 +801,8 @@ var ReactCompositeComponent = {
 
 };
 
+// Temporary injection.
+// TODO: Delete this hack once implementation details are hidden.
+instantiateReactComponent._compositeBase = ReactCompositeComponentBase;
+
 module.exports = ReactCompositeComponent;
diff --git a/src/core/ReactElement.js b/src/core/ReactElement.js
index dd7c86ba31b..098ab88a845 100644
--- a/src/core/ReactElement.js
+++ b/src/core/ReactElement.js
@@ -199,6 +199,7 @@ ReactElement.createFactory = function(type) {
   // easily accessed on elements. E.g. <Foo />.type === Foo.type.
   // This should not be named `constructor` since this may not be the function
   // that created the element, and it may not even be a constructor.
+  // Legacy hook TODO: Warn if this is accessed
   factory.type = type;
   return factory;
 };
diff --git a/src/core/ReactElementValidator.js b/src/core/ReactElementValidator.js
index 84f8b547292..0469e8ca45f 100644
--- a/src/core/ReactElementValidator.js
+++ b/src/core/ReactElementValidator.js
@@ -273,6 +273,7 @@ var ReactElementValidator = {
       null,
       type
     );
+    // Legacy hook TODO: Warn if this is accessed
     validatedFactory.type = type;
     return validatedFactory;
   }
diff --git a/src/core/ReactLegacyElement.js b/src/core/ReactLegacyElement.js
deleted file mode 100644
index 67b9c7fb6bb..00000000000
--- a/src/core/ReactLegacyElement.js
+++ /dev/null
@@ -1,243 +0,0 @@
-/**
- * Copyright 2014, Facebook, Inc.
- * All rights reserved.
- *
- * This source code is licensed under the BSD-style license found in the
- * LICENSE file in the root directory of this source tree. An additional grant
- * of patent rights can be found in the PATENTS file in the same directory.
- *
- * @providesModule ReactLegacyElement
- */
-
-"use strict";
-
-var ReactCurrentOwner = require('ReactCurrentOwner');
-
-var invariant = require('invariant');
-var monitorCodeUse = require('monitorCodeUse');
-var warning = require('warning');
-
-var legacyFactoryLogs = {};
-function warnForLegacyFactoryCall() {
-  if (!ReactLegacyElementFactory._isLegacyCallWarningEnabled) {
-    return;
-  }
-  var owner = ReactCurrentOwner.current;
-  var name = owner && owner.constructor ? owner.constructor.displayName : '';
-  if (!name) {
-    name = 'Something';
-  }
-  if (legacyFactoryLogs.hasOwnProperty(name)) {
-    return;
-  }
-  legacyFactoryLogs[name] = true;
-  warning(
-    false,
-    name + ' is calling a React component directly. ' +
-    'Use a factory or JSX instead. See: http://fb.me/react-legacyfactory'
-  );
-  monitorCodeUse('react_legacy_factory_call', { version: 3, name: name });
-}
-
-function warnForPlainFunctionType(type) {
-  var isReactClass =
-    type.prototype &&
-    typeof type.prototype.mountComponent === 'function' &&
-    typeof type.prototype.receiveComponent === 'function';
-  if (isReactClass) {
-    warning(
-      false,
-      'Did not expect to get a React class here. Use `Component` instead ' +
-      'of `Component.type` or `this.constructor`.'
-    );
-  } else {
-    if (!type._reactWarnedForThisType) {
-      try {
-        type._reactWarnedForThisType = true;
-      } catch (x) {
-        // just incase this is a frozen object or some special object
-      }
-      monitorCodeUse(
-        'react_non_component_in_jsx',
-        { version: 3, name: type.name }
-      );
-    }
-    warning(
-      false,
-      'This JSX uses a plain function. Only React components are ' +
-      'valid in React\'s JSX transform.'
-    );
-  }
-}
-
-function warnForNonLegacyFactory(type) {
-  warning(
-    false,
-    'Do not pass React.DOM.' + type.type + ' to JSX or createFactory. ' +
-    'Use the string "' + type.type + '" instead.'
-  );
-}
-
-/**
- * Transfer static properties from the source to the target. Functions are
- * rebound to have this reflect the original source.
- */
-function proxyStaticMethods(target, source) {
-  if (typeof source !== 'function') {
-    return;
-  }
-  for (var key in source) {
-    if (source.hasOwnProperty(key)) {
-      var value = source[key];
-      if (typeof value === 'function') {
-        var bound = value.bind(source);
-        // Copy any properties defined on the function, such as `isRequired` on
-        // a PropTypes validator.
-        for (var k in value) {
-          if (value.hasOwnProperty(k)) {
-            bound[k] = value[k];
-          }
-        }
-        target[key] = bound;
-      } else {
-        target[key] = value;
-      }
-    }
-  }
-}
-
-// We use an object instead of a boolean because booleans are ignored by our
-// mocking libraries when these factories gets mocked.
-var LEGACY_MARKER = {};
-var NON_LEGACY_MARKER = {};
-
-var ReactLegacyElementFactory = {};
-
-ReactLegacyElementFactory.wrapCreateFactory = function(createFactory) {
-  var legacyCreateFactory = function(type) {
-    if (typeof type !== 'function') {
-      // Non-function types cannot be legacy factories
-      return createFactory(type);
-    }
-
-    if (type.isReactNonLegacyFactory) {
-      // This is probably a factory created by ReactDOM we unwrap it to get to
-      // the underlying string type. It shouldn't have been passed here so we
-      // warn.
-      if (__DEV__) {
-        warnForNonLegacyFactory(type);
-      }
-      return createFactory(type.type);
-    }
-
-    if (type.isReactLegacyFactory) {
-      // This is probably a legacy factory created by ReactCompositeComponent.
-      // We unwrap it to get to the underlying class.
-      return createFactory(type.type);
-    }
-
-    if (__DEV__) {
-      warnForPlainFunctionType(type);
-    }
-
-    // Unless it's a legacy factory, then this is probably a plain function,
-    // that is expecting to be invoked by JSX. We can just return it as is.
-    return type;
-  };
-  return legacyCreateFactory;
-};
-
-ReactLegacyElementFactory.wrapCreateElement = function(createElement) {
-  var legacyCreateElement = function(type, props, children) {
-    if (typeof type !== 'function') {
-      // Non-function types cannot be legacy factories
-      return createElement.apply(this, arguments);
-    }
-
-    var args;
-
-    if (type.isReactNonLegacyFactory) {
-      // This is probably a factory created by ReactDOM we unwrap it to get to
-      // the underlying string type. It shouldn't have been passed here so we
-      // warn.
-      if (__DEV__) {
-        warnForNonLegacyFactory(type);
-      }
-      args = Array.prototype.slice.call(arguments, 0);
-      args[0] = type.type;
-      return createElement.apply(this, args);
-    }
-
-    if (type.isReactLegacyFactory) {
-      // This is probably a legacy factory created by ReactCompositeComponent.
-      // We unwrap it to get to the underlying class.
-      if (type._isMockFunction) {
-        // If this is a mock function, people will expect it to be called. We
-        // will actually call the original mock factory function instead. This
-        // future proofs unit testing that assume that these are classes.
-        type.type._mockedReactClassConstructor = type;
-      }
-      args = Array.prototype.slice.call(arguments, 0);
-      args[0] = type.type;
-      return createElement.apply(this, args);
-    }
-
-    if (__DEV__) {
-      warnForPlainFunctionType(type);
-    }
-
-    // This is being called with a plain function we should invoke it
-    // immediately as if this was used with legacy JSX.
-    return type.apply(null, Array.prototype.slice.call(arguments, 1));
-  };
-  return legacyCreateElement;
-};
-
-ReactLegacyElementFactory.wrapFactory = function(factory) {
-  invariant(
-    typeof factory === 'function',
-    'This is suppose to accept a element factory'
-  );
-  var legacyElementFactory = function(config, children) {
-    // This factory should not be called when JSX is used. Use JSX instead.
-    if (__DEV__) {
-      warnForLegacyFactoryCall();
-    }
-    return factory.apply(this, arguments);
-  };
-  proxyStaticMethods(legacyElementFactory, factory.type);
-  legacyElementFactory.isReactLegacyFactory = LEGACY_MARKER;
-  legacyElementFactory.type = factory.type;
-  return legacyElementFactory;
-};
-
-// This is used to mark a factory that will remain. E.g. we're allowed to call
-// it as a function. However, you're not suppose to pass it to createElement
-// or createFactory, so it will warn you if you do.
-ReactLegacyElementFactory.markNonLegacyFactory = function(factory) {
-  factory.isReactNonLegacyFactory = NON_LEGACY_MARKER;
-  return factory;
-};
-
-// Checks if a factory function is actually a legacy factory pretending to
-// be a class.
-ReactLegacyElementFactory.isValidFactory = function(factory) {
-  // TODO: This will be removed and moved into a class validator or something.
-  return typeof factory === 'function' &&
-    factory.isReactLegacyFactory === LEGACY_MARKER;
-};
-
-ReactLegacyElementFactory.isValidClass = function(factory) {
-  if (__DEV__) {
-    warning(
-      false,
-      'isValidClass is deprecated and will be removed in a future release. ' +
-      'Use a more specific validator instead.'
-    );
-  }
-  return ReactLegacyElementFactory.isValidFactory(factory);
-};
-
-ReactLegacyElementFactory._isLegacyCallWarningEnabled = true;
-
-module.exports = ReactLegacyElementFactory;
diff --git a/src/core/ReactNativeComponent.js b/src/core/ReactNativeComponent.js
index ba485d61476..5bc49b0a6fa 100644
--- a/src/core/ReactNativeComponent.js
+++ b/src/core/ReactNativeComponent.js
@@ -58,7 +58,7 @@ function createInstanceForTag(tag, props, parentType) {
     return new genericComponentClass(tag, props);
   }
   // Unwrap legacy factories
-  return new componentClass.type(props);
+  return new componentClass(props);
 }
 
 var ReactNativeComponent = {
diff --git a/src/core/__tests__/ReactCompositeComponent-test.js b/src/core/__tests__/ReactCompositeComponent-test.js
index b87db3b21fe..cf94ce86b88 100644
--- a/src/core/__tests__/ReactCompositeComponent-test.js
+++ b/src/core/__tests__/ReactCompositeComponent-test.js
@@ -878,51 +878,6 @@ describe('ReactCompositeComponent', function() {
     expect(ReactMount.purgeID.callCount).toBe(4);
   });
 
-  it('should warn but detect valid CompositeComponent classes', function() {
-    var warn = console.warn;
-    console.warn = mocks.getMockFunction();
-
-    var Component = React.createClass({
-      render: function() {
-        return <div/>;
-      }
-    });
-
-    expect(React.isValidClass(Component)).toBe(true);
-
-    expect(console.warn.mock.calls.length).toBe(1);
-    expect(console.warn.mock.calls[0][0]).toContain(
-      'isValidClass is deprecated and will be removed in a future release'
-    );
-  });
-
-  it('should warn but detect invalid CompositeComponent classes', function() {
-    var warn = console.warn;
-    console.warn = mocks.getMockFunction();
-
-    var FnComponent = function() {
-      return false;
-    };
-
-    var NullComponent = null;
-
-    var TrickFnComponent = function() {
-      return true;
-    };
-    TrickFnComponent.componentConstructor = true;
-
-    expect(React.isValidClass(FnComponent)).toBe(false);
-    expect(React.isValidClass(NullComponent)).toBe(false);
-    expect(React.isValidClass(TrickFnComponent)).toBe(false);
-
-    expect(console.warn.mock.calls.length).toBe(3);
-    console.warn.mock.calls.forEach(function(call) {
-      expect(call[0]).toContain(
-        'isValidClass is deprecated and will be removed in a future release'
-      );
-    });
-  });
-
   it('should warn when shouldComponentUpdate() returns undefined', function() {
     var warn = console.warn;
     console.warn = mocks.getMockFunction();
@@ -1282,8 +1237,8 @@ describe('ReactCompositeComponent', function() {
     expect(Component.ghi).toBe(null);
     expect(instance.constructor.jkl).toBe('mno');
     expect(Component.jkl).toBe('mno');
-    expect(instance.constructor.pqr()).toBe(Component.type);
-    expect(Component.pqr()).toBe(Component.type);
+    expect(instance.constructor.pqr()).toBe(Component);
+    expect(Component.pqr()).toBe(Component);
   });
 
   it('should throw if a reserved property is in statics', function() {
diff --git a/src/core/__tests__/ReactCompositeComponentMixin-test.js b/src/core/__tests__/ReactCompositeComponentMixin-test.js
index f3878d2998a..f76e657b768 100644
--- a/src/core/__tests__/ReactCompositeComponentMixin-test.js
+++ b/src/core/__tests__/ReactCompositeComponentMixin-test.js
@@ -152,8 +152,8 @@ describe('ReactCompositeComponent-mixin', function() {
   });
 
   it('should validate prop types via mixins', function() {
-    expect(TestComponent.type.propTypes).toBeDefined();
-    expect(TestComponent.type.propTypes.value)
+    expect(TestComponent.propTypes).toBeDefined();
+    expect(TestComponent.propTypes.value)
       .toBe(mixinPropValidator);
   });
 
@@ -161,11 +161,11 @@ describe('ReactCompositeComponent-mixin', function() {
     // Sanity check...
     expect(componentPropValidator).toNotBe(mixinPropValidator);
     // Actually check...
-    expect(TestComponentWithPropTypes.type.propTypes)
+    expect(TestComponentWithPropTypes.propTypes)
       .toBeDefined();
-    expect(TestComponentWithPropTypes.type.propTypes.value)
+    expect(TestComponentWithPropTypes.propTypes.value)
       .toNotBe(mixinPropValidator);
-    expect(TestComponentWithPropTypes.type.propTypes.value)
+    expect(TestComponentWithPropTypes.propTypes.value)
       .toBe(componentPropValidator);
   });
 });
diff --git a/src/core/__tests__/ReactCompositeComponentSpec-test.js b/src/core/__tests__/ReactCompositeComponentSpec-test.js
index b9fc2c9d6bd..63f5ff277eb 100644
--- a/src/core/__tests__/ReactCompositeComponentSpec-test.js
+++ b/src/core/__tests__/ReactCompositeComponentSpec-test.js
@@ -41,7 +41,7 @@ describe('ReactCompositeComponent-spec', function() {
       }
     });
 
-    expect(TestComponent.type.displayName)
+    expect(TestComponent.displayName)
       .toBe('TestComponent');
   });
 
@@ -56,8 +56,8 @@ describe('ReactCompositeComponent-spec', function() {
       }
     });
 
-    expect(TestComponent.type.propTypes).toBeDefined();
-    expect(TestComponent.type.propTypes.value)
+    expect(TestComponent.propTypes).toBeDefined();
+    expect(TestComponent.propTypes.value)
       .toBe(propValidator);
   });
 });
diff --git a/src/core/__tests__/ReactElement-test.js b/src/core/__tests__/ReactElement-test.js
index 74bfa726aff..faf967dc6b3 100644
--- a/src/core/__tests__/ReactElement-test.js
+++ b/src/core/__tests__/ReactElement-test.js
@@ -26,7 +26,7 @@ describe('ReactElement', function() {
     ComponentFactory = React.createClass({
       render: function() { return <div />; }
     });
-    ComponentClass = ComponentFactory.type;
+    ComponentClass = ComponentFactory;
   });
 
   it('returns a complete element according to spec', function() {
@@ -338,52 +338,6 @@ describe('ReactElement', function() {
     expect(ReactElement.isValidElement(Component)).toEqual(false);
   });
 
-  it('warns but allow a plain function in a factory to be invoked', function() {
-    spyOn(console, 'warn');
-    // This is a temporary helper to allow JSX with plain functions.
-    // This allow you to track down these callers and replace them with regular
-    // function calls.
-    var factory = React.createFactory(function (x) {
-      return 21 + x;
-    });
-    expect(factory(21)).toBe(42);
-    expect(console.warn.argsForCall.length).toBe(1);
-    expect(console.warn.argsForCall[0][0]).toContain(
-      'This JSX uses a plain function.'
-    );
-  });
-
-  it('warns but allow a plain function to be immediately invoked', function() {
-    spyOn(console, 'warn');
-    var result = React.createElement(function (x, y) {
-      return 21 + x + y;
-    }, 11, 10);
-    expect(result).toBe(42);
-    expect(console.warn.argsForCall.length).toBe(1);
-    expect(console.warn.argsForCall[0][0]).toContain(
-      'This JSX uses a plain function.'
-    );
-  });
-
-  it('warns but does not fail on undefined results', function() {
-    spyOn(console, 'warn');
-    var fn = function () { };
-    var result = React.createElement(fn, 1, 2, null);
-    expect(result).toBe(undefined);
-    expect(console.warn.argsForCall.length).toBe(1);
-    expect(console.warn.argsForCall[0][0]).toContain(
-      'This JSX uses a plain function.'
-    );
-  });
-
-
-  it('should expose the underlying class from a legacy factory', function() {
-    var Legacy = React.createClass({ render: function() { } });
-    var factory = React.createFactory(Legacy);
-    expect(factory.type).toBe(Legacy.type);
-    expect(factory().type).toBe(Legacy.type);
-  });
-
   it('allows the use of PropTypes validators in statics', function() {
     var Component = React.createClass({
       render: () => null,
diff --git a/src/core/__tests__/ReactMockedComponent-test.js b/src/core/__tests__/ReactMockedComponent-test.js
new file mode 100644
index 00000000000..970fcb702dd
--- /dev/null
+++ b/src/core/__tests__/ReactMockedComponent-test.js
@@ -0,0 +1,138 @@
+/**
+ * Copyright 2013-2014, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @emails react-core
+ */
+
+"use strict";
+
+var React;
+var ReactComponent;
+var ReactTestUtils;
+
+var reactComponentExpect;
+var mocks;
+
+var OriginalComponent;
+var AutoMockedComponent;
+var MockedComponent;
+
+describe('ReactMockedComponent', function() {
+
+  beforeEach(function() {
+    mocks = require('mocks');
+
+    React = require('React');
+    ReactComponent = require('ReactComponent');
+    ReactTestUtils = require('ReactTestUtils');
+
+    OriginalComponent = React.createClass({
+
+      getInitialState: function() {
+        return { foo: 'bar' };
+      },
+
+      hasCustomMethod: function() {
+        return true;
+      },
+
+      render: function() {
+        return <span />;
+      }
+
+    });
+
+    var metaData = mocks.getMetadata(OriginalComponent);
+
+    AutoMockedComponent = mocks.generateFromMetadata(metaData);
+    MockedComponent = mocks.generateFromMetadata(metaData);
+
+    ReactTestUtils.mockComponent(MockedComponent);
+  });
+
+  it('should allow an implicitly mocked component to be rendered', () => {
+    ReactTestUtils.renderIntoDocument(<AutoMockedComponent />);
+  });
+
+  it('should allow an implicitly mocked component to be updated', () => {
+    var Wrapper = React.createClass({
+
+      getInitialState: function() {
+        return { foo: 1 };
+      },
+
+      update: function() {
+        this.setState({ foo: 2 });
+      },
+
+      render: function() {
+        return <AutoMockedComponent prop={this.state.foo} />;
+      }
+
+    });
+    var instance = ReactTestUtils.renderIntoDocument(<Wrapper />);
+    instance.update();
+  });
+
+  it('should find an implicitly mocked component in the tree', function() {
+    var instance = ReactTestUtils.renderIntoDocument(
+      <div><span><AutoMockedComponent prop="1" /></span></div>
+    );
+    var found = ReactTestUtils.findRenderedComponentWithType(
+      instance,
+      AutoMockedComponent
+    );
+    expect(typeof found).toBe('object');
+  });
+
+  it('has custom methods on the implicitly mocked component', () => {
+    var instance = ReactTestUtils.renderIntoDocument(<AutoMockedComponent />);
+    expect(typeof instance.hasCustomMethod).toBe('function');
+  });
+
+  it('should allow an explicitly mocked component to be rendered', () => {
+    ReactTestUtils.renderIntoDocument(<MockedComponent />);
+  });
+
+  it('should allow an explicitly mocked component to be updated', () => {
+    var Wrapper = React.createClass({
+
+      getInitialState: function() {
+        return { foo: 1 };
+      },
+
+      update: function() {
+        this.setState({ foo: 2 });
+      },
+
+      render: function() {
+        return <MockedComponent prop={this.state.foo} />;
+      }
+
+    });
+    var instance = ReactTestUtils.renderIntoDocument(<Wrapper />);
+    instance.update();
+  });
+
+  it('should find an explicitly mocked component in the tree', function() {
+    var instance = ReactTestUtils.renderIntoDocument(
+      <div><span><MockedComponent prop="1" /></span></div>
+    );
+    var found = ReactTestUtils.findRenderedComponentWithType(
+      instance,
+      MockedComponent
+    );
+    expect(typeof found).toBe('object');
+  });
+
+  it('has custom methods on the explicitly mocked component', () => {
+    var instance = ReactTestUtils.renderIntoDocument(<MockedComponent />);
+    expect(typeof instance.hasCustomMethod).toBe('function');
+  });
+
+});
diff --git a/src/core/instantiateReactComponent.js b/src/core/instantiateReactComponent.js
index a43f722e03f..ab5f3800f70 100644
--- a/src/core/instantiateReactComponent.js
+++ b/src/core/instantiateReactComponent.js
@@ -15,9 +15,29 @@
 var warning = require('warning');
 
 var ReactElement = require('ReactElement');
-var ReactLegacyElement = require('ReactLegacyElement');
 var ReactNativeComponent = require('ReactNativeComponent');
-var ReactEmptyComponent = require('ReactEmptyComponent');
+
+// This is temporary until we've hidden all the implementation details
+// TODO: Delete this hack once implementation details are hidden
+var publicAPIs = {
+  forceUpdate: true,
+  replaceState: true,
+  setProps: true,
+  setState: true,
+  getDOMNode: true
+  // Public APIs used internally:
+  // isMounted: true,
+  // replaceProps: true,
+};
+
+function unmockImplementationDetails(mockInstance) {
+  var ReactCompositeComponentBase = instantiateReactComponent._compositeBase;
+  for (var key in ReactCompositeComponentBase.prototype) {
+    if (!publicAPIs.hasOwnProperty(key)) {
+      mockInstance[key] = ReactCompositeComponentBase.prototype[key];
+    }
+  }
+}
 
 /**
  * Given an `element` create an instance that will actually be mounted.
@@ -36,47 +56,6 @@ function instantiateReactComponent(element, parentCompositeType) {
                      typeof element.type === 'string'),
       'Only functions or strings can be mounted as React components.'
     );
-
-    // Resolve mock instances
-    if (element.type._mockedReactClassConstructor) {
-      // If this is a mocked class, we treat the legacy factory as if it was the
-      // class constructor for future proofing unit tests. Because this might
-      // be mocked as a legacy factory, we ignore any warnings triggerd by
-      // this temporary hack.
-      ReactLegacyElement._isLegacyCallWarningEnabled = false;
-      try {
-        instance = new element.type._mockedReactClassConstructor(
-          element.props
-        );
-      } finally {
-        ReactLegacyElement._isLegacyCallWarningEnabled = true;
-      }
-
-      // If the mock implementation was a legacy factory, then it returns a
-      // element. We need to turn this into a real component instance.
-      if (ReactElement.isValidElement(instance)) {
-        instance = new instance.type(instance.props);
-      }
-
-      var render = instance.render;
-      if (!render) {
-        // For auto-mocked factories, the prototype isn't shimmed and therefore
-        // there is no render function on the instance. We replace the whole
-        // component with an empty component instance instead.
-        element = ReactEmptyComponent.getEmptyComponent();
-      } else {
-        if (render._isMockFunction && !render._getMockImplementation()) {
-          // Auto-mocked components may have a prototype with a mocked render
-          // function. For those, we'll need to mock the result of the render
-          // since we consider undefined to be invalid results from render.
-          render.mockImplementation(
-            ReactEmptyComponent.getEmptyComponent
-          );
-        }
-        instance.construct(element);
-        return instance;
-      }
-    }
   }
 
   // Special case string values
@@ -92,6 +71,11 @@ function instantiateReactComponent(element, parentCompositeType) {
   }
 
   if (__DEV__) {
+    if (element.type._isMockFunction) {
+      // TODO: Remove this special case
+      unmockImplementationDetails(instance);
+    }
+
     warning(
       typeof instance.construct === 'function' &&
       typeof instance.mountComponent === 'function' &&
diff --git a/src/test/ReactTestUtils.js b/src/test/ReactTestUtils.js
index 43cf273ec69..3e2deccc86a 100644
--- a/src/test/ReactTestUtils.js
+++ b/src/test/ReactTestUtils.js
@@ -55,7 +55,7 @@ var ReactTestUtils = {
   isElementOfType: function(inst, convenienceConstructor) {
     return (
       ReactElement.isValidElement(inst) &&
-      inst.type === convenienceConstructor.type
+      inst.type === convenienceConstructor
     );
   },
 
@@ -76,7 +76,7 @@ var ReactTestUtils = {
 
   isCompositeComponentWithType: function(inst, type) {
     return !!(ReactTestUtils.isCompositeComponent(inst) &&
-             (inst.constructor === type.type));
+             (inst.constructor === type));
   },
 
   isCompositeComponentElement: function(inst) {
@@ -231,21 +231,14 @@ var ReactTestUtils = {
   mockComponent: function(module, mockTagName) {
     mockTagName = mockTagName || module.mockTagName || "div";
 
-    var ConvenienceConstructor = React.createClass({
-      render: function() {
-        return React.createElement(
-          mockTagName,
-          null,
-          this.props.children
-        );
-      }
+    module.prototype.render.mockImplementation(function() {
+      return React.createElement(
+        mockTagName,
+        null,
+        this.props.children
+      );
     });
 
-    module.mockImplementation(ConvenienceConstructor);
-
-    module.type = ConvenienceConstructor.type;
-    module.isReactLegacyFactory = true;
-
     return this;
   },
 
diff --git a/src/test/reactComponentExpect.js b/src/test/reactComponentExpect.js
index c788682f659..cb03a48b3a0 100644
--- a/src/test/reactComponentExpect.js
+++ b/src/test/reactComponentExpect.js
@@ -97,12 +97,9 @@ assign(reactComponentExpect.prototype, {
 
   // Matchers ------------------------------------------------------------------
 
-  toBeComponentOfType: function(convenienceConstructor) {
-    var type = typeof convenienceConstructor === 'string' ?
-               convenienceConstructor :
-               convenienceConstructor.type;
+  toBeComponentOfType: function(constructor) {
     expect(
-      this.instance()._currentElement.type === type
+      this.instance()._currentElement.type === constructor
     ).toBe(true);
     return this;
   },
@@ -119,10 +116,10 @@ assign(reactComponentExpect.prototype, {
     return this;
   },
 
-  toBeCompositeComponentWithType: function(convenienceConstructor) {
+  toBeCompositeComponentWithType: function(constructor) {
     this.toBeCompositeComponent();
     expect(
-      this.instance()._currentElement.type === convenienceConstructor.type
+      this.instance()._currentElement.type === constructor
     ).toBe(true);
     return this;
   },