diff --git a/src/browser/ReactTextComponent.js b/src/browser/ReactTextComponent.js
index c8080dc233..f1e71151af 100644
--- a/src/browser/ReactTextComponent.js
+++ b/src/browser/ReactTextComponent.js
@@ -45,6 +45,16 @@ var ReactTextComponent = function(initialText) {
   this.construct({text: initialText});
 };
 
+/**
+ * Used to clone the text descriptor object before it's mounted.
+ *
+ * @param {object} props
+ * @return {object} A new ReactTextComponent instance
+ */
+ReactTextComponent.ConvenienceConstructor = function(props) {
+  return new ReactTextComponent(props.text);
+};
+
 mixInto(ReactTextComponent, ReactComponent.Mixin);
 mixInto(ReactTextComponent, ReactBrowserComponentMixin);
 mixInto(ReactTextComponent, {
diff --git a/src/browser/server/ReactServerRendering.js b/src/browser/server/ReactServerRendering.js
index 5dc221c710..056eca4eac 100644
--- a/src/browser/server/ReactServerRendering.js
+++ b/src/browser/server/ReactServerRendering.js
@@ -24,7 +24,7 @@ var ReactMarkupChecksum = require('ReactMarkupChecksum');
 var ReactServerRenderingTransaction =
   require('ReactServerRenderingTransaction');
 
-
+var instantiateReactComponent = require('instantiateReactComponent');
 var invariant = require('invariant');
 
 /**
@@ -49,7 +49,8 @@ function renderComponentToString(component) {
     transaction = ReactServerRenderingTransaction.getPooled(false);
 
     return transaction.perform(function() {
-      var markup = component.mountComponent(id, transaction, 0);
+      var componentInstance = instantiateReactComponent(component);
+      var markup = componentInstance.mountComponent(id, transaction, 0);
       return ReactMarkupChecksum.addChecksumToMarkup(markup);
     }, null);
   } finally {
diff --git a/src/browser/ui/ReactMount.js b/src/browser/ui/ReactMount.js
index ccc993f5a1..f98409abb5 100644
--- a/src/browser/ui/ReactMount.js
+++ b/src/browser/ui/ReactMount.js
@@ -25,6 +25,7 @@ var ReactPerf = require('ReactPerf');
 
 var containsNode = require('containsNode');
 var getReactRootElementInContainer = require('getReactRootElementInContainer');
+var instantiateReactComponent = require('instantiateReactComponent');
 var invariant = require('invariant');
 var shouldUpdateReactComponent = require('shouldUpdateReactComponent');
 
@@ -296,8 +297,13 @@ var ReactMount = {
         nextComponent,
         container,
         shouldReuseMarkup) {
-      var reactRootID = ReactMount._registerComponent(nextComponent, container);
-      nextComponent.mountComponentIntoNode(
+
+      var componentInstance = instantiateReactComponent(nextComponent);
+      var reactRootID = ReactMount._registerComponent(
+        componentInstance,
+        container
+      );
+      componentInstance.mountComponentIntoNode(
         reactRootID,
         container,
         shouldReuseMarkup
@@ -309,7 +315,7 @@ var ReactMount = {
           getReactRootElementInContainer(container);
       }
 
-      return nextComponent;
+      return componentInstance;
     }
   ),
 
diff --git a/src/core/ReactCompositeComponent.js b/src/core/ReactCompositeComponent.js
index efc8f8d2ef..ffade81194 100644
--- a/src/core/ReactCompositeComponent.js
+++ b/src/core/ReactCompositeComponent.js
@@ -29,6 +29,7 @@ var ReactPropTypeLocations = require('ReactPropTypeLocations');
 var ReactPropTypeLocationNames = require('ReactPropTypeLocationNames');
 var ReactUpdates = require('ReactUpdates');
 
+var instantiateReactComponent = require('instantiateReactComponent');
 var invariant = require('invariant');
 var keyMirror = require('keyMirror');
 var merge = require('merge');
@@ -595,19 +596,52 @@ if (__DEV__) {
     constructor: true,
     construct: true,
     isOwnedBy: true, // should be deprecated but can have code mod (internal)
-    mountComponent: true,
-    mountComponentIntoNode: true,
-    props: true,
     type: true,
-    _checkPropTypes: true,
-    _mountComponentIntoNode: true,
-    _processContext: true
+    props: true,
+    // currently private but belong on the descriptor and are valid for use
+    // inside the framework:
+    __keyValidated__: true,
+    _owner: true,
+    _currentContext: true
+  };
+
+  var componentInstanceProperties = {
+    __keyValidated__: true,
+    __keySetters: true,
+    _compositeLifeCycleState: true,
+    _currentContext: true,
+    _defaultProps: true,
+    _instance: true,
+    _lifeCycleState: true,
+    _mountDepth: true,
+    _owner: true,
+    _pendingCallbacks: true,
+    _pendingContext: true,
+    _pendingForceUpdate: true,
+    _pendingOwner: true,
+    _pendingProps: true,
+    _pendingState: true,
+    _renderedComponent: true,
+    _rootNodeID: true,
+    context: true,
+    props: true,
+    refs: true,
+    state: true,
+
+    // These are known instance properties coming from other sources
+    _pendingQueries: true,
+    _queryPropListeners: true,
+    queryParams: true
+
   };
 
   var hasWarnedOnComponentType = {};
 
-  var warnIfUnmounted = function(instance, key) {
-    if (instance.__hasBeenMounted) {
+  var warningStackCounter = 0;
+
+  var issueMembraneWarning = function(instance, key) {
+    var isWhitelisted = unmountedPropertyWhitelist.hasOwnProperty(key);
+    if (warningStackCounter > 0 || isWhitelisted) {
       return;
     }
     var name = instance.constructor.displayName || 'Unknown';
@@ -631,6 +665,30 @@ if (__DEV__) {
     );
   };
 
+  var wrapInMembraneFunction = function(fn, thisBinding) {
+    if (fn.__reactMembraneFunction && fn.__reactMembraneSelf === thisBinding) {
+      return fn.__reactMembraneFunction;
+    }
+    return fn.__reactMembraneFunction = function() {
+      /**
+       * By getting this function, you've already received a warning. The
+       * internals of this function will likely cause more warnings. To avoid
+       * Spamming too much we disable any warning triggered inside of this
+       * stack.
+       */
+      warningStackCounter++;
+      try {
+        // If the this binding is unchanged, we defer to the real component.
+        // This is important to keep some referential integrity in the
+        // internals. E.g. owner equality check.
+        var self = this === thisBinding ? this.__realComponentInstance : this;
+        return fn.apply(self, arguments);
+      } finally {
+        warningStackCounter--;
+      }
+    };
+  };
+
   var defineMembraneProperty = function(membrane, prototype, key) {
     Object.defineProperty(membrane, key, {
 
@@ -638,31 +696,33 @@ if (__DEV__) {
       enumerable: true,
 
       get: function() {
-        if (this !== membrane) {
-          // When this is accessed through a prototype chain we need to check if
-          // this component was mounted.
-          warnIfUnmounted(this, key);
+        if (this === membrane) {
+          // We're allowed to access the prototype directly.
+          return prototype[key];
         }
-        return prototype[key];
+        issueMembraneWarning(this, key);
+
+        var realValue = this.__realComponentInstance[key];
+        // If the real value is a function, we need to provide a wrapper that
+        // disables nested warnings. The properties type and constructors are
+        // expected to the be constructors and therefore is often use with an
+        // equality check and we shouldn't try to rebind those.
+        if (typeof realValue === 'function' &&
+            key !== 'type' &&
+            key !== 'constructor') {
+          return wrapInMembraneFunction(realValue, this);
+        }
+        return realValue;
       },
 
       set: function(value) {
-        if (this !== membrane) {
-          // When this is accessed through a prototype chain, we first check if
-          // this component was mounted. Then we define a value on "this"
-          // instance, effectively disabling the membrane on that prototype
-          // chain.
-          warnIfUnmounted(this, key);
-          Object.defineProperty(this, key, {
-            enumerable: true,
-            configurable: true,
-            writable: true,
-            value: value
-          });
-        } else {
-          // Otherwise, this should modify the prototype
+        if (this === membrane) {
+          // We're allowed to set a value on the prototype directly.
           prototype[key] = value;
+          return;
         }
+        issueMembraneWarning(this, key);
+        this.__realComponentInstance[key] = value;
       }
 
     });
@@ -677,26 +737,51 @@ if (__DEV__) {
    * @private
    */
   var createMountWarningMembrane = function(prototype) {
-    try {
-      var membrane = Object.create(prototype);
-      for (var key in prototype) {
-        if (unmountedPropertyWhitelist.hasOwnProperty(key)) {
-          continue;
-        }
+    var membrane = {};
+    var key;
+    for (key in prototype) {
+      defineMembraneProperty(membrane, prototype, key);
+    }
+    // These are properties that goes into the instance but not the prototype.
+    // We can create the membrane on the prototype even though this will
+    // result in a faulty hasOwnProperty check it's better perf.
+    for (key in componentInstanceProperties) {
+      if (componentInstanceProperties.hasOwnProperty(key) &&
+          !(key in prototype)) {
         defineMembraneProperty(membrane, prototype, key);
       }
+    }
+    return membrane;
+  };
 
-      membrane.mountComponent = function() {
-        this.__hasBeenMounted = true;
-        return prototype.mountComponent.apply(this, arguments);
+  /**
+   * Creates a membrane constructor which wraps the component that gets mounted.
+   *
+   * @param {function} constructor Original constructor.
+   * @return {function} The membrane constructor.
+   * @private
+   */
+  var createDescriptorProxy = function(constructor) {
+    try {
+      var ProxyConstructor = function() {
+        this.__realComponentInstance = new constructor();
+
+        // We can only safely pass through known instance variables. Unknown
+        // expandos are not safe. Use the real mounted instance to avoid this
+        // problem if it blows something up.
+        Object.freeze(this);
       };
 
-      return membrane;
+      ProxyConstructor.prototype = createMountWarningMembrane(
+        constructor.prototype
+      );
+
+      return ProxyConstructor;
     } catch(x) {
       // In IE8 define property will fail on non-DOM objects. If anything in
-      // the membrane creation fails, we'll bail out and just use the prototype
-      // without warnings.
-      return prototype;
+      // the membrane creation fails, we'll bail out and just use the plain
+      // constructor without warnings.
+      return constructor;
     }
   };
 
@@ -772,13 +857,29 @@ var ReactCompositeComponentMixin = {
     this.state = null;
     this._pendingState = null;
 
-    this.context = this._processContext(ReactContext.current);
+    this.context = null;
     this._currentContext = ReactContext.current;
     this._pendingContext = null;
 
+    // The descriptor that was used to instantiate this component. Will be
+    // set by the instantiator instead of the constructor since this
+    // constructor is currently used by both instances and descriptors.
+    this._descriptor = null;
+
     this._compositeLifeCycleState = null;
   },
 
+  /**
+   * Components in the intermediate state now has cyclic references. To avoid
+   * breaking JSON serialization we expose a custom JSON format.
+   * @return {object} JSON compatible representation.
+   * @internal
+   * @final
+   */
+  toJSON: function() {
+    return { type: this.type, props: this.props };
+  },
+
   /**
    * Checks whether or not this composite component is mounted.
    * @return {boolean} True if mounted, false otherwise.
@@ -812,6 +913,7 @@ var ReactCompositeComponentMixin = {
       );
       this._compositeLifeCycleState = CompositeLifeCycle.MOUNTING;
 
+      this.context = this._processContext(this._currentContext);
       this._defaultProps = this.getDefaultProps ? this.getDefaultProps() : null;
       this.props = this._processProps(this.props);
 
@@ -839,7 +941,9 @@ var ReactCompositeComponentMixin = {
         }
       }
 
-      this._renderedComponent = this._renderValidatedComponent();
+      this._renderedComponent = instantiateReactComponent(
+        this._renderValidatedComponent()
+      );
 
       // Done with mounting, `setState` will now trigger UI changes.
       this._compositeLifeCycleState = null;
@@ -1173,13 +1277,16 @@ var ReactCompositeComponentMixin = {
   },
 
   receiveComponent: function(nextComponent, transaction) {
-    if (nextComponent === this) {
+    if (nextComponent === this._descriptor) {
       // Since props and context are immutable after the component is
       // mounted, we can do a cheap identity compare here to determine
       // if this is a superfluous reconcile.
       return;
     }
 
+    // Update the descriptor that was last used by this component instance
+    this._descriptor = nextComponent;
+
     this._pendingContext = nextComponent._currentContext;
     ReactComponent.Mixin.receiveComponent.call(
       this,
@@ -1212,17 +1319,19 @@ var ReactCompositeComponentMixin = {
         prevProps,
         prevOwner
       );
-      var prevComponent = this._renderedComponent;
+
+
+      var prevComponentInstance = this._renderedComponent;
       var nextComponent = this._renderValidatedComponent();
-      if (shouldUpdateReactComponent(prevComponent, nextComponent)) {
-        prevComponent.receiveComponent(nextComponent, transaction);
+      if (shouldUpdateReactComponent(prevComponentInstance, nextComponent)) {
+        prevComponentInstance.receiveComponent(nextComponent, transaction);
       } else {
         // These two IDs are actually the same! But nothing should rely on that.
         var thisID = this._rootNodeID;
-        var prevComponentID = prevComponent._rootNodeID;
-        prevComponent.unmountComponent();
-        this._renderedComponent = nextComponent;
-        var nextMarkup = nextComponent.mountComponent(
+        var prevComponentID = prevComponentInstance._rootNodeID;
+        prevComponentInstance.unmountComponent();
+        this._renderedComponent = instantiateReactComponent(nextComponent);
+        var nextMarkup = this._renderedComponent.mountComponent(
           thisID,
           transaction,
           this._mountDepth + 1
@@ -1401,10 +1510,12 @@ var ReactCompositeComponent = {
     Constructor.prototype = new ReactCompositeComponentBase();
     Constructor.prototype.constructor = Constructor;
 
+    var DescriptorConstructor = Constructor;
+
     var ConvenienceConstructor = function(props, children) {
-      var instance = new Constructor();
-      instance.construct.apply(instance, arguments);
-      return instance;
+      var descriptor = new DescriptorConstructor();
+      descriptor.construct.apply(descriptor, arguments);
+      return descriptor;
     };
     ConvenienceConstructor.componentConstructor = Constructor;
     Constructor.ConvenienceConstructor = ConvenienceConstructor;
@@ -1452,7 +1563,10 @@ var ReactCompositeComponent = {
     }
 
     if (__DEV__) {
-      Constructor.prototype = createMountWarningMembrane(Constructor.prototype);
+      // In DEV the convenience constructor generates a proxy to another
+      // instance around it to warn about access to properties on the
+      // descriptor.
+      DescriptorConstructor = createDescriptorProxy(Constructor);
     }
 
     return ConvenienceConstructor;
diff --git a/src/core/ReactMultiChild.js b/src/core/ReactMultiChild.js
index 22a54b7b5b..8cc6c10106 100644
--- a/src/core/ReactMultiChild.js
+++ b/src/core/ReactMultiChild.js
@@ -23,6 +23,7 @@ var ReactComponent = require('ReactComponent');
 var ReactMultiChildUpdateTypes = require('ReactMultiChildUpdateTypes');
 
 var flattenChildren = require('flattenChildren');
+var instantiateReactComponent = require('instantiateReactComponent');
 var shouldUpdateReactComponent = require('shouldUpdateReactComponent');
 
 /**
@@ -192,14 +193,18 @@ var ReactMultiChild = {
       for (var name in children) {
         var child = children[name];
         if (children.hasOwnProperty(name)) {
+          // The rendered children must be turned into instances as they're
+          // mounted.
+          var childInstance = instantiateReactComponent(child);
+          children[name] = childInstance;
           // Inlined for performance, see `ReactInstanceHandles.createReactID`.
           var rootID = this._rootNodeID + name;
-          var mountImage = child.mountComponent(
+          var mountImage = childInstance.mountComponent(
             rootID,
             transaction,
             this._mountDepth + 1
           );
-          child._mountIndex = index;
+          childInstance._mountIndex = index;
           mountImages.push(mountImage);
           index++;
         }
@@ -293,8 +298,10 @@ var ReactMultiChild = {
             lastIndex = Math.max(prevChild._mountIndex, lastIndex);
             this._unmountChildByName(prevChild, name);
           }
+          // The child must be instantiated before it's mounted.
+          var nextChildInstance = instantiateReactComponent(nextChild);
           this._mountChildByNameAtIndex(
-            nextChild, name, nextIndex, transaction
+            nextChildInstance, name, nextIndex, transaction
           );
         }
         nextIndex++;
diff --git a/src/core/__tests__/ReactBind-test.js b/src/core/__tests__/ReactBind-test.js
index 00743a04f6..ef5b93c3b2 100644
--- a/src/core/__tests__/ReactBind-test.js
+++ b/src/core/__tests__/ReactBind-test.js
@@ -61,13 +61,13 @@ describe('autobinding', function() {
     });
 
     var instance1 = <TestBindComponent />;
-    ReactTestUtils.renderIntoDocument(instance1);
+    var mountedInstance1 = ReactTestUtils.renderIntoDocument(instance1);
     var rendered1 = reactComponentExpect(instance1)
       .expectRenderedChild()
       .instance();
 
     var instance2 = <TestBindComponent />;
-    ReactTestUtils.renderIntoDocument(instance2);
+    var mountedInstance2 = ReactTestUtils.renderIntoDocument(instance2);
     var rendered2 = reactComponentExpect(instance2)
       .expectRenderedChild()
       .instance();
@@ -77,25 +77,25 @@ describe('autobinding', function() {
       badIdea();
     }).toThrow();
 
-    expect(instance1.onMouseEnter).toBe(instance2.onMouseEnter);
-    expect(instance1.onMouseLeave).toBe(instance2.onMouseLeave);
-    expect(instance1.onClick).not.toBe(instance2.onClick);
+    expect(mountedInstance1.onMouseEnter).toBe(mountedInstance2.onMouseEnter);
+    expect(mountedInstance1.onMouseLeave).toBe(mountedInstance2.onMouseLeave);
+    expect(mountedInstance1.onClick).not.toBe(mountedInstance2.onClick);
 
     ReactTestUtils.Simulate.click(rendered1);
     expect(mouseDidClick.mock.instances.length).toBe(1);
-    expect(mouseDidClick.mock.instances[0]).toBe(instance1);
+    expect(mouseDidClick.mock.instances[0]).toBe(mountedInstance1);
 
     ReactTestUtils.Simulate.click(rendered2);
     expect(mouseDidClick.mock.instances.length).toBe(2);
-    expect(mouseDidClick.mock.instances[1]).toBe(instance2);
+    expect(mouseDidClick.mock.instances[1]).toBe(mountedInstance2);
 
     ReactTestUtils.Simulate.mouseOver(rendered1);
     expect(mouseDidEnter.mock.instances.length).toBe(1);
-    expect(mouseDidEnter.mock.instances[0]).toBe(instance1);
+    expect(mouseDidEnter.mock.instances[0]).toBe(mountedInstance1);
 
     ReactTestUtils.Simulate.mouseOver(rendered2);
     expect(mouseDidEnter.mock.instances.length).toBe(2);
-    expect(mouseDidEnter.mock.instances[1]).toBe(instance2);
+    expect(mouseDidEnter.mock.instances[1]).toBe(mountedInstance2);
 
     ReactTestUtils.Simulate.mouseOut(rendered1);
     expect(mouseDidLeave.mock.instances.length).toBe(1);
@@ -122,14 +122,14 @@ describe('autobinding', function() {
     });
 
     var instance1 = <TestBindComponent />;
-    ReactTestUtils.renderIntoDocument(instance1);
+    var mountedInstance1 = ReactTestUtils.renderIntoDocument(instance1);
     var rendered1 = reactComponentExpect(instance1)
       .expectRenderedChild()
       .instance();
 
     ReactTestUtils.Simulate.click(rendered1);
     expect(mouseDidClick.mock.instances.length).toBe(1);
-    expect(mouseDidClick.mock.instances[0]).toBe(instance1);
+    expect(mouseDidClick.mock.instances[0]).toBe(mountedInstance1);
   });
 
 });
diff --git a/src/core/__tests__/ReactComponentLifeCycle-test.js b/src/core/__tests__/ReactComponentLifeCycle-test.js
index a2163e826e..ae35b942ee 100644
--- a/src/core/__tests__/ReactComponentLifeCycle-test.js
+++ b/src/core/__tests__/ReactComponentLifeCycle-test.js
@@ -312,9 +312,7 @@ describe('ReactComponentLifeCycle', function() {
     // A component that is merely "constructed" (as in "constructor") but not
     // yet initialized, or rendered.
     //
-    var instance = <LifeCycleComponent />;
-    expect(instance._lifeCycleState).toBe(ComponentLifeCycle.UNMOUNTED);
-    ReactTestUtils.renderIntoDocument(instance);
+    var instance = ReactTestUtils.renderIntoDocument(<LifeCycleComponent />);
 
     // getInitialState
     expect(instance._testJournal.returnedFromGetInitialState).toEqual(
diff --git a/src/core/__tests__/ReactCompositeComponent-test.js b/src/core/__tests__/ReactCompositeComponent-test.js
index d6141e9d48..f42b0054f9 100644
--- a/src/core/__tests__/ReactCompositeComponent-test.js
+++ b/src/core/__tests__/ReactCompositeComponent-test.js
@@ -183,21 +183,23 @@ describe('ReactCompositeComponent', function() {
 
     // Next, prove that once mounted, the scope is bound correctly to the actual
     // component.
-    ReactTestUtils.renderIntoDocument(instance);
+    var mountedInstance = ReactTestUtils.renderIntoDocument(instance);
     expect(console.warn.argsForCall.length).toBe(3);
+    // This will result in a warning that has already been issued before.
     var explicitlyBound = instance.methodToBeExplicitlyBound.bind(instance);
-    expect(console.warn.argsForCall.length).toBe(4);
+    expect(console.warn.argsForCall.length).toBe(3);
     var autoBound = instance.methodAutoBound;
     var explicitlyNotBound = instance.methodExplicitlyNotBound;
 
     var context = {};
-    expect(explicitlyBound.call(context)).toBe(instance);
-    expect(autoBound.call(context)).toBe(instance);
+    expect(explicitlyBound.call(context)).toBe(mountedInstance);
+    expect(autoBound.call(context)).toBe(mountedInstance);
     expect(explicitlyNotBound.call(context)).toBe(context);
 
-    expect(explicitlyBound.call(instance)).toBe(instance);
-    expect(autoBound.call(instance)).toBe(instance);
-    expect(explicitlyNotBound.call(instance)).toBe(instance);
+    expect(explicitlyBound.call(instance)).toBe(mountedInstance);
+    expect(autoBound.call(instance)).toBe(mountedInstance);
+    // This one is the weird one
+    expect(explicitlyNotBound.call(instance)).toBe(mountedInstance);
 
   });
 
@@ -279,8 +281,7 @@ describe('ReactCompositeComponent', function() {
       }
     });
 
-    var instance = <Component />;
-    ReactTestUtils.renderIntoDocument(instance);
+    var instance = ReactTestUtils.renderIntoDocument(<Component />);
     reactComponentExpect(instance).scalarPropsEqual({key: 'testKey'});
     reactComponentExpect(instance).scalarStateEqual({key: 'testKeyState'});
 
@@ -1179,9 +1180,8 @@ describe('ReactCompositeComponent', function() {
     expect(console.warn.argsForCall.length).toBe(0);
 
     var unmountedInstance = <ComponentClass />;
-    var result = unmountedInstance.someMethod();
+    unmountedInstance.someMethod();
     expect(console.warn.argsForCall.length).toBe(1);
-    expect(result).toBe(unmountedInstance);
 
     var unmountedInstance2 = <ComponentClass />;
     unmountedInstance2.someOtherMethod = 'override';
diff --git a/src/core/instantiateReactComponent.js b/src/core/instantiateReactComponent.js
new file mode 100644
index 0000000000..750b13fda8
--- /dev/null
+++ b/src/core/instantiateReactComponent.js
@@ -0,0 +1,70 @@
+/**
+ * Copyright 2013-2014 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * @providesModule instantiateReactComponent
+ * @typechecks static-only
+ */
+
+"use strict";
+
+var warning = require('warning');
+
+/**
+ * Validate a `componentDescriptor`. This should be exposed publicly in a follow
+ * up diff.
+ *
+ * @param {object} descriptor
+ * @return {boolean} Returns true if this is a valid descriptor of a Component.
+ */
+function isValidComponentDescriptor(descriptor) {
+  return (
+    typeof descriptor.constructor === 'function' &&
+    typeof descriptor.constructor.prototype.construct === 'function' &&
+    typeof descriptor.constructor.prototype.mountComponent === 'function' &&
+    typeof descriptor.constructor.prototype.receiveComponent === 'function'
+  );
+}
+
+/**
+ * Given a `componentDescriptor` create an instance that will actually be
+ * mounted. Currently it just extracts an existing clone from composite
+ * components but this is an implementation detail which will change.
+ *
+ * @param {object} descriptor
+ * @return {object} A new instance of componentDescriptor's constructor.
+ * @protected
+ */
+function instantiateReactComponent(descriptor) {
+  if (__DEV__) {
+    warning(
+      isValidComponentDescriptor(descriptor),
+      'Only React Components are valid for mounting.'
+    );
+    // We use the clone of a composite component instead of the original
+    // instance. This allows us to warn you if you're are accessing the wrong
+    // instance.
+    var instance = descriptor.__realComponentInstance || descriptor;
+    instance._descriptor = descriptor;
+    return instance;
+  }
+  // In prod we don't clone, we simply use the same instance for unaffected
+  // behavior. We have to keep the descriptor around for comparison later on.
+  // This should ideally be accepted in the constructor of the instance but
+  // since that is currently overloaded, we just manually attach it here.
+  descriptor._descriptor = descriptor;
+  return descriptor;
+}
+
+module.exports = instantiateReactComponent;
diff --git a/src/core/shouldUpdateReactComponent.js b/src/core/shouldUpdateReactComponent.js
index 07781cc59a..c2ee9a4030 100644
--- a/src/core/shouldUpdateReactComponent.js
+++ b/src/core/shouldUpdateReactComponent.js
@@ -20,33 +20,36 @@
 "use strict";
 
 /**
- * Given a `prevComponent` and `nextComponent`, determines if `prevComponent`
- * should be updated as opposed to being destroyed or replaced.
+ * Given a `prevComponentInstance` and `nextComponent`, determines if
+ * `prevComponentInstance` should be updated as opposed to being destroyed or
+ * replaced by a new instance. The second argument is a descriptor. Future
+ * versions of the reconciler should only compare descriptors to other
+ * descriptors.
  *
- * @param {?object} prevComponent
- * @param {?object} nextComponent
- * @return {boolean} True if `prevComponent` should be updated.
+ * @param {?object} prevComponentInstance
+ * @param {?object} nextDescriptor
+ * @return {boolean} True if `prevComponentInstance` should be updated.
  * @protected
  */
-function shouldUpdateReactComponent(prevComponent, nextComponent) {
+function shouldUpdateReactComponent(prevComponentInstance, nextDescriptor) {
   // TODO: Remove warning after a release.
-  if (prevComponent && nextComponent &&
-      prevComponent.constructor === nextComponent.constructor && (
-        (prevComponent.props && prevComponent.props.key) ===
-        (nextComponent.props && nextComponent.props.key)
+  if (prevComponentInstance && nextDescriptor &&
+      prevComponentInstance.constructor === nextDescriptor.constructor && (
+        (prevComponentInstance.props && prevComponentInstance.props.key) ===
+        (nextDescriptor.props && nextDescriptor.props.key)
       )) {
-    if (prevComponent._owner === nextComponent._owner) {
+    if (prevComponentInstance._owner === nextDescriptor._owner) {
       return true;
     } else {
       if (__DEV__) {
-        if (prevComponent.state) {
+        if (prevComponentInstance.state) {
           console.warn(
             'A recent change to React has been found to impact your code. ' +
             'A mounted component will now be unmounted and replaced by a ' +
             'component (of the same class) if their owners are different. ' +
             'Previously, ownership was not considered when updating.',
-            prevComponent,
-            nextComponent
+            prevComponentInstance,
+            nextDescriptor
           );
         }
       }
diff --git a/src/utils/traverseAllChildren.js b/src/utils/traverseAllChildren.js
index 2fa6861f34..379d6e98f1 100644
--- a/src/utils/traverseAllChildren.js
+++ b/src/utils/traverseAllChildren.js
@@ -126,7 +126,8 @@ var traverseAllChildrenImpl =
         // All of the above are perceived as null.
         callback(traverseContext, null, storageName, indexSoFar);
         subtreeCount = 1;
-      } else if (children.mountComponentIntoNode) {
+      } else if (children.type && children.type.prototype &&
+                 children.type.prototype.mountComponentIntoNode) {
         callback(traverseContext, children, storageName, indexSoFar);
         subtreeCount = 1;
       } else {