diff --git a/.flowconfig b/.flowconfig
index 94ffcb54a2..d15db1c9ab 100644
--- a/.flowconfig
+++ b/.flowconfig
@@ -34,4 +34,4 @@ suppress_comment=\\(.\\|\n\\)*\\$FlowIssue\\((\\(>=0\\.\\(2[0-4]\\|1[0-9]\\|[0-9
 suppress_comment=\\(.\\|\n\\)*\\$FlowFixedInNextDeploy
 
 [version]
-^0.26.0
+^0.27.0
diff --git a/package.json b/package.json
index afa8ed8947..67ac99e5f8 100644
--- a/package.json
+++ b/package.json
@@ -43,7 +43,7 @@
     "eslint-plugin-react-internal": "file:eslint-rules",
     "fbjs": "^0.8.1",
     "fbjs-scripts": "^0.6.0",
-    "flow-bin": "^0.26.0",
+    "flow-bin": "^0.27.0",
     "glob": "^6.0.1",
     "grunt": "^0.4.5",
     "grunt-cli": "^0.1.13",
diff --git a/src/renderers/noop/ReactNoop.js b/src/renderers/noop/ReactNoop.js
index 4ffa0b6582..5682dc9f8a 100644
--- a/src/renderers/noop/ReactNoop.js
+++ b/src/renderers/noop/ReactNoop.js
@@ -27,18 +27,53 @@ var ReactFiberReconciler = require('ReactFiberReconciler');
 var scheduledHighPriCallback = null;
 var scheduledLowPriCallback = null;
 
+const TERMINAL_TAG = 99;
+
+type Container = { rootID: number, children: Array<Instance> };
 type Props = { };
-type Instance = { id: number };
+type Instance = { tag: 99, type: string, id: number, children: Array<Instance> };
 
 var instanceCounter = 0;
 
+function recursivelyAppendChildren(flatArray : Array<Instance>, child : HostChildren<Instance>) {
+  if (!child) {
+    return;
+  }
+  if (child.tag === TERMINAL_TAG) {
+    flatArray.push(child);
+  } else {
+    let node = child;
+    do {
+      recursivelyAppendChildren(flatArray, node.output);
+    } while (node = node.sibling);
+  }
+}
+
+function flattenChildren(children : HostChildren<Instance>) {
+  const flatArray = [];
+  recursivelyAppendChildren(flatArray, children);
+  return flatArray;
+}
+
 var NoopRenderer = ReactFiberReconciler({
 
+  updateContainer(containerInfo : Container, children : HostChildren<Instance>) : void {
+    console.log('Update container #' + containerInfo.rootID);
+    containerInfo.children = flattenChildren(children);
+  },
+
   createInstance(type : string, props : Props, children : HostChildren<Instance>) : Instance {
     console.log('Create instance #' + instanceCounter);
-    return {
-      id: instanceCounter++
+    const inst = {
+      tag: TERMINAL_TAG,
+      id: instanceCounter++,
+      type: type,
+      children: flattenChildren(children),
     };
+    // Hide from unit tests
+    Object.defineProperty(inst, 'tag', { value: inst.tag, enumerable: false });
+    Object.defineProperty(inst, 'id', { value: inst.id, enumerable: false });
+    return inst;
   },
 
   prepareUpdate(instance : Instance, oldProps : Props, newProps : Props, children : HostChildren<Instance>) : boolean {
@@ -48,6 +83,7 @@ var NoopRenderer = ReactFiberReconciler({
 
   commitUpdate(instance : Instance, oldProps : Props, newProps : Props, children : HostChildren<Instance>) : void {
     console.log('Commit update on #' + instance.id);
+    instance.children = flattenChildren(children);
   },
 
   deleteInstance(instance : Instance) : void {
@@ -64,13 +100,17 @@ var NoopRenderer = ReactFiberReconciler({
 
 });
 
+var rootContainer = { rootID: 0, children: [] };
+
 var root = null;
 
 var ReactNoop = {
 
+  root: rootContainer,
+
   render(element : ReactElement<any>) {
     if (!root) {
-      root = NoopRenderer.mountContainer(element, null);
+      root = NoopRenderer.mountContainer(element, rootContainer);
     } else {
       NoopRenderer.updateContainer(element, root);
     }
@@ -115,6 +155,19 @@ var ReactNoop = {
       console.log('Nothing rendered yet.');
       return;
     }
+
+    function logHostInstances(children: Array<Instance>, depth) {
+      for (var i = 0; i < children.length; i++) {
+        var child = children[i];
+        console.log('  '.repeat(depth) + '- ' + child.type + '#' + child.id);
+        logHostInstances(child.children, depth + 1);
+      }
+    }
+    function logContainer(container : Container, depth) {
+      console.log('  '.repeat(depth) + '- [root#' + container.rootID + ']');
+      logHostInstances(container.children, depth + 1);
+    }
+
     function logFiber(fiber : Fiber, depth) {
       console.log('  '.repeat(depth) + '- ' + (fiber.type ? fiber.type.name || fiber.type : '[root]'), '[' + fiber.pendingWorkPriority + (fiber.pendingProps ? '*' : '') + ']');
       if (fiber.child) {
@@ -124,6 +177,10 @@ var ReactNoop = {
         logFiber(fiber.sibling, depth);
       }
     }
+
+    console.log('HOST INSTANCES:');
+    logContainer(rootContainer, 0);
+    console.log('FIBERS:');
     logFiber((root.stateNode : any).current, 0);
   },
 
diff --git a/src/renderers/shared/fiber/ReactFiberBeginWork.js b/src/renderers/shared/fiber/ReactFiberBeginWork.js
index 4de8ce2d5b..4fcf4d87b0 100644
--- a/src/renderers/shared/fiber/ReactFiberBeginWork.js
+++ b/src/renderers/shared/fiber/ReactFiberBeginWork.js
@@ -34,7 +34,7 @@ var {
 } = require('ReactPriorityLevel');
 var { findNextUnitOfWorkAtPriority } = require('ReactFiberPendingWork');
 
-module.exports = function<T, P, I>(config : HostConfig<T, P, I>) {
+module.exports = function<T, P, I, C>(config : HostConfig<T, P, I, C>) {
 
   function reconcileChildren(current, workInProgress, nextChildren) {
     const priority = workInProgress.pendingWorkPriority;
diff --git a/src/renderers/shared/fiber/ReactFiberCommitWork.js b/src/renderers/shared/fiber/ReactFiberCommitWork.js
index 1f3e5e5a22..9f27e76ae9 100644
--- a/src/renderers/shared/fiber/ReactFiberCommitWork.js
+++ b/src/renderers/shared/fiber/ReactFiberCommitWork.js
@@ -13,6 +13,7 @@
 'use strict';
 
 import type { Fiber } from 'ReactFiber';
+import type { FiberRoot } from 'ReactFiberRoot';
 import type { HostConfig } from 'ReactFiberReconciler';
 
 var ReactTypeOfWork = require('ReactTypeOfWork');
@@ -22,23 +23,31 @@ var {
   HostComponent,
 } = ReactTypeOfWork;
 
-module.exports = function<T, P, I>(config : HostConfig<T, P, I>) {
+module.exports = function<T, P, I, C>(config : HostConfig<T, P, I, C>) {
 
+  const updateContainer = config.updateContainer;
   const commitUpdate = config.commitUpdate;
 
   function commitWork(finishedWork : Fiber) : void {
     switch (finishedWork.tag) {
-      case ClassComponent:
+      case ClassComponent: {
         // TODO: Fire componentDidMount/componentDidUpdate, update refs
         return;
-      case HostContainer:
+      }
+      case HostContainer: {
         // TODO: Attach children to root container.
+        const children = finishedWork.output;
+        const root : FiberRoot = finishedWork.stateNode;
+        const containerInfo : C = root.containerInfo;
+        updateContainer(containerInfo, children);
         return;
-      case HostComponent:
+      }
+      case HostComponent: {
         if (finishedWork.stateNode == null || !finishedWork.alternate) {
           throw new Error('This should only be done during updates.');
         }
-        const children = finishedWork.output;
+        const child = (finishedWork.child : ?Fiber);
+        const children = (child && !child.sibling) ? (child.output : ?Fiber | I) : child;
         const newProps = finishedWork.memoizedProps;
         // If we have an alternate, that means this is an update and we need to
         // schedule a side-effect to do the updates.
@@ -47,6 +56,7 @@ module.exports = function<T, P, I>(config : HostConfig<T, P, I>) {
         const instance : I = finishedWork.stateNode;
         commitUpdate(instance, oldProps, newProps, children);
         return;
+      }
       default:
         throw new Error('This unit of work tag should not have side-effects.');
     }
diff --git a/src/renderers/shared/fiber/ReactFiberCompleteWork.js b/src/renderers/shared/fiber/ReactFiberCompleteWork.js
index 6f4752ccc0..c91ecfa82c 100644
--- a/src/renderers/shared/fiber/ReactFiberCompleteWork.js
+++ b/src/renderers/shared/fiber/ReactFiberCompleteWork.js
@@ -17,6 +17,8 @@ import type { Fiber } from 'ReactFiber';
 import type { HostConfig } from 'ReactFiberReconciler';
 import type { ReifiedYield } from 'ReactReifiedYield';
 
+import type { TypeOfWork } from 'ReactTypeOfWork';
+
 var ReactChildFiber = require('ReactChildFiber');
 var ReactTypeOfWork = require('ReactTypeOfWork');
 var {
@@ -30,7 +32,7 @@ var {
   YieldComponent,
 } = ReactTypeOfWork;
 
-module.exports = function<T, P, I>(config : HostConfig<T, P, I>) {
+module.exports = function<T, P, I, C>(config : HostConfig<T, P, I, C>) {
 
   const createInstance = config.createInstance;
   const prepareUpdate = config.prepareUpdate;
@@ -120,12 +122,22 @@ module.exports = function<T, P, I>(config : HostConfig<T, P, I>) {
         transferOutput(workInProgress.child, workInProgress);
         return null;
       case HostContainer:
+        transferOutput(workInProgress.child, workInProgress);
+        // We don't know if a container has updated any children so we always
+        // need to update it right now. We schedule this side-effect after
+        // all the other side-effects in the subtree.
+        // TODO: I just realized that this means that nodes are not in the DOM
+        // document when componentDidMount/Update fires. I'll need to change
+        // the order for host component effects to happen *before* their
+        // children I think.
+        markForPostEffect(workInProgress);
         return null;
       case HostComponent:
         console.log('/host component', workInProgress.type);
-        transferOutput(workInProgress.child, workInProgress);
-        const children = workInProgress.output;
-        const newProps = workInProgress.memoizedProps;
+        const child = (workInProgress.child : ?Fiber);
+        const children = (child && !child.sibling) ? (child.output : ?Fiber | I) : child;
+        const newProps = workInProgress.pendingProps;
+        workInProgress.memoizedProps = newProps;
         if (workInProgress.alternate && workInProgress.stateNode != null) {
           // If we have an alternate, that means this is an update and we need to
           // schedule a side-effect to do the updates.
@@ -136,9 +148,12 @@ module.exports = function<T, P, I>(config : HostConfig<T, P, I>) {
             // This returns true if there was something to update.
             markForPostEffect(workInProgress);
           }
+          workInProgress.output = instance;
         } else {
           const instance = createInstance(workInProgress.type, newProps, children);
+          // TODO: This seems like unnecessary duplication.
           workInProgress.stateNode = instance;
+          workInProgress.output = instance;
         }
         return null;
       case CoroutineComponent:
diff --git a/src/renderers/shared/fiber/ReactFiberReconciler.js b/src/renderers/shared/fiber/ReactFiberReconciler.js
index 28421314ab..cb22e88421 100644
--- a/src/renderers/shared/fiber/ReactFiberReconciler.js
+++ b/src/renderers/shared/fiber/ReactFiberReconciler.js
@@ -14,6 +14,7 @@
 
 import type { Fiber } from 'ReactFiber';
 import type { FiberRoot } from 'ReactFiberRoot';
+import type { TypeOfWork } from 'ReactTypeOfWork';
 
 var { createFiberRoot } = require('ReactFiberRoot');
 var ReactFiberScheduler = require('ReactFiberScheduler');
@@ -26,11 +27,17 @@ type Deadline = {
   timeRemaining : () => number
 };
 
-type HostChildNode<I> = { output: HostChildren<I>, sibling: ?HostChildNode<I> };
+type HostChildNode<I> = { tag: TypeOfWork, output: HostChildren<I>, sibling: any };
 
 export type HostChildren<I> = null | void | I | HostChildNode<I>;
 
-export type HostConfig<T, P, I> = {
+export type HostConfig<T, P, I, C> = {
+
+  // TODO: We don't currently have a quick way to detect that children didn't
+  // reorder so we host will always need to check the set. We should make a flag
+  // or something so that it can bailout easily.
+
+  updateContainer(containerInfo : C, children : HostChildren<I>) : void;
 
   createInstance(type : T, props : P, children : HostChildren<I>) : I,
   prepareUpdate(instance : I, oldProps : P, newProps : P, children : HostChildren<I>) : bool,
@@ -44,22 +51,22 @@ export type HostConfig<T, P, I> = {
 
 type OpaqueNode = Fiber;
 
-export type Reconciler = {
-  mountContainer(element : ReactElement<any>, containerInfo : ?Object) : OpaqueNode,
+export type Reconciler<C> = {
+  mountContainer(element : ReactElement<any>, containerInfo : C) : OpaqueNode,
   updateContainer(element : ReactElement<any>, container : OpaqueNode) : void,
   unmountContainer(container : OpaqueNode) : void,
 
   // Used to extract the return value from the initial render. Legacy API.
-  getPublicRootInstance(container : OpaqueNode) : ?Object,
+  getPublicRootInstance(container : OpaqueNode) : (C | null),
 };
 
-module.exports = function<T, P, I>(config : HostConfig<T, P, I>) : Reconciler {
+module.exports = function<T, P, I, C>(config : HostConfig<T, P, I, C>) : Reconciler<C> {
 
   var { scheduleLowPriWork } = ReactFiberScheduler(config);
 
   return {
 
-    mountContainer(element : ReactElement<any>, containerInfo : ?Object) : OpaqueNode {
+    mountContainer(element : ReactElement<any>, containerInfo : C) : OpaqueNode {
       const root = createFiberRoot(containerInfo);
       const container = root.current;
       // TODO: Use pending work/state instead of props.
@@ -94,7 +101,7 @@ module.exports = function<T, P, I>(config : HostConfig<T, P, I>) : Reconciler {
       scheduleLowPriWork(root);
     },
 
-    getPublicRootInstance(container : OpaqueNode) : ?Object {
+    getPublicRootInstance(container : OpaqueNode) : (C | null) {
       return null;
     },
 
diff --git a/src/renderers/shared/fiber/ReactFiberRoot.js b/src/renderers/shared/fiber/ReactFiberRoot.js
index ce186c3fce..c0b312253c 100644
--- a/src/renderers/shared/fiber/ReactFiberRoot.js
+++ b/src/renderers/shared/fiber/ReactFiberRoot.js
@@ -18,7 +18,7 @@ const { createHostContainerFiber } = require('ReactFiber');
 
 export type FiberRoot = {
   // Any additional information from the host associated with this root.
-  containerInfo: ?Object,
+  containerInfo: any,
   // The currently active root fiber. This is the mutable root of the tree.
   current: Fiber,
   // Determines if this root has already been added to the schedule for work.
@@ -27,7 +27,7 @@ export type FiberRoot = {
   nextScheduledRoot: ?FiberRoot,
 };
 
-exports.createFiberRoot = function(containerInfo : ?Object) : FiberRoot {
+exports.createFiberRoot = function(containerInfo : any) : FiberRoot {
   // Cyclic construction. This cheats the type system right now because
   // stateNode is any.
   const uninitializedFiber = createHostContainerFiber();
diff --git a/src/renderers/shared/fiber/ReactFiberScheduler.js b/src/renderers/shared/fiber/ReactFiberScheduler.js
index c3aab11536..6df6198f9f 100644
--- a/src/renderers/shared/fiber/ReactFiberScheduler.js
+++ b/src/renderers/shared/fiber/ReactFiberScheduler.js
@@ -32,7 +32,7 @@ var {
 
 var timeHeuristicForUnitOfWork = 1;
 
-module.exports = function<T, P, I>(config : HostConfig<T, P, I>) {
+module.exports = function<T, P, I, C>(config : HostConfig<T, P, I, C>) {
 
   const { beginWork } = ReactFiberBeginWork(config);
   const { completeWork } = ReactFiberCompleteWork(config);
diff --git a/src/renderers/shared/fiber/__tests__/ReactIncrementalSideEffects-test.js b/src/renderers/shared/fiber/__tests__/ReactIncrementalSideEffects-test.js
new file mode 100644
index 0000000000..c59c12b97d
--- /dev/null
+++ b/src/renderers/shared/fiber/__tests__/ReactIncrementalSideEffects-test.js
@@ -0,0 +1,97 @@
+/**
+ * Copyright 2013-present, 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 ReactNoop;
+
+describe('ReactIncremental', function() {
+  beforeEach(function() {
+    React = require('React');
+    ReactNoop = require('ReactNoop');
+    spyOn(console, 'log');
+  });
+
+  function div(...children) {
+    return { type: 'div', children };
+  }
+
+  function span(...children) {
+    return { type: 'span', children };
+  }
+
+  it('can update child nodes of a host instance', function() {
+
+    function Bar(props) {
+      return <span>{props.text}</span>;
+    }
+
+    function Foo(props) {
+      return (
+        <div>
+          <Bar text={props.text} />
+          {props.text === 'World' ? <Bar text={props.text} /> : null}
+        </div>
+      );
+    }
+
+    ReactNoop.render(<Foo text="Hello" />);
+    ReactNoop.flush();
+    expect(ReactNoop.root.children).toEqual([
+      div(span()),
+    ]);
+
+    ReactNoop.render(<Foo text="World" />);
+    ReactNoop.flush();
+    expect(ReactNoop.root.children).toEqual([
+      div(span(), span()),
+    ]);
+
+  });
+
+  it('does not update child nodes if a flush is aborted', function() {
+
+    function Bar(props) {
+      return <span>{props.text}</span>;
+    }
+
+    function Foo(props) {
+      return (
+        <div>
+          <div>
+            <Bar text={props.text} />
+            {props.text === 'Hello' ? <Bar text={props.text} /> : null}
+          </div>
+          <Bar text="Yo" />
+        </div>
+      );
+    }
+
+    ReactNoop.render(<Foo text="Hello" />);
+    ReactNoop.flush();
+    expect(ReactNoop.root.children).toEqual([
+      div(div(span(), span()), span()),
+    ]);
+
+    ReactNoop.render(<Foo text="World" />);
+    ReactNoop.flushLowPri(35);
+    expect(ReactNoop.root.children).toEqual([
+      div(div(span(), span()), span()),
+    ]);
+
+  });
+
+  // TODO: Test that side-effects are not cut off when a work in progress node
+  // moves to "current" without flushing due to having lower priority. Does this
+  // even happen? Maybe a child doesn't get processed because it is lower prio?
+
+});