diff --git a/blocks/api/categories.js b/blocks/api/categories.js
index bb6e3576e92c70..4757cd932531cd 100644
--- a/blocks/api/categories.js
+++ b/blocks/api/categories.js
@@ -13,7 +13,8 @@ import { __ } from 'i18n';
  */
 const categories = [
 	{ slug: 'common', title: __( 'Common Blocks' ) },
-	{ slug: 'layout', title: __( 'Layout Blocks' ) }
+	{ slug: 'layout', title: __( 'Layout Blocks' ) },
+	{ slug: 'social', title: __( 'Social Media' ) }
 ];
 
 /**
diff --git a/blocks/library/embed/index.js b/blocks/library/embed/index.js
index 5e153f33f2a1c6..dbb80fb0dda966 100644
--- a/blocks/library/embed/index.js
+++ b/blocks/library/embed/index.js
@@ -32,7 +32,7 @@ registerBlock( 'core/embed', {
 		if ( ! url ) {
 			return (
 				<Placeholder icon="cloud" label={ wp.i18n.__( 'Embed URL' ) } className="blocks-embed">
-					<input type="url" className="placeholder__input" placeholder={ wp.i18n.__( 'Enter URL to embed here...' ) } />
+					<input type="url" className="components-placeholder__input" placeholder={ wp.i18n.__( 'Enter URL to embed…' ) } />
 					<Button isLarge>
 						{ wp.i18n.__( 'Embed' ) }
 					</Button>
diff --git a/blocks/library/index.js b/blocks/library/index.js
index 655e7ab40dd43b..c5704219d56752 100644
--- a/blocks/library/index.js
+++ b/blocks/library/index.js
@@ -8,3 +8,4 @@ import './quote';
 import './separator';
 import './button';
 import './pullquote';
+import './tweet';
diff --git a/blocks/library/tweet/index.js b/blocks/library/tweet/index.js
new file mode 100644
index 00000000000000..ba4432ce7effd3
--- /dev/null
+++ b/blocks/library/tweet/index.js
@@ -0,0 +1,112 @@
+/**
+ * External dependencies
+ */
+import jQuery from 'jquery';
+/**
+ * WordPress dependencies
+ */
+import Sandbox from 'components/sandbox';
+import Button from 'components/button';
+import Placeholder from 'components/placeholder';
+/**
+ * Internal dependencies
+ */
+import { registerBlock } from '../../api';
+
+registerBlock( 'core/tweet', {
+	title: wp.i18n.__( 'Tweet' ),
+	icon: 'twitter',
+
+	category: 'social',
+
+	attributes( url ) {
+		return { url };
+	},
+
+	edit: class extends wp.element.Component {
+		constructor() {
+			super( ...arguments );
+			this.fetchTweet = this.fetchTweet.bind( this );
+			// Copies the block's url so we can edit it without having the block
+			// update (i.e. refetch the tweet) every time it changes in this edit component.
+			this.state = {
+				url: this.props.attributes.url,
+				html: '',
+				error: false,
+				fetching: false,
+			};
+		}
+		doFetch( url ) {
+			this.setState( { fetching: true, error: false } );
+			this.fetchXHR = jQuery.ajax( {
+				type: 'GET',
+				dataType: 'jsonp',
+				timeout: 5000,
+				url: 'https://publish.twitter.com/oembed?url=' + encodeURI( url ),
+				error: () => this.setState( { fetching: false, error: true } ),
+				success: ( msg ) => {
+					this.props.setAttributes( { url } );
+					this.setState( { fetching: false, error: false, html: msg.html } );
+				},
+			} );
+		}
+		componentDidMount() {
+			if ( this.state.url ) {
+				this.doFetch( this.state.url );
+			}
+		}
+		componentWillUnmount() {
+			if ( this.fetchXHR ) {
+				this.fetchXHR.abort();
+				delete this.fetchXHR;
+			}
+		}
+		fetchTweet( event ) {
+			const { url } = this.state;
+			event.preventDefault();
+			this.doFetch( url );
+		}
+		render() {
+			const { html, url, error, fetching } = this.state;
+
+			if ( html ) {
+				/* translators: %s: url of the tweet */
+				const title = wp.i18n.sprintf( wp.i18n.__( 'Embedded from %s' ), url );
+				return (
+					<Sandbox
+						html={ html }
+						title={ title } />
+				);
+			}
+
+			return (
+				<Placeholder icon="twitter" label={ wp.i18n.__( 'Twitter' ) } className="blocks-tweet">
+					<form onSubmit={ this.fetchTweet }>
+						<input
+							className="components-placeholder__input"
+							value={ url }
+							placeholder={ wp.i18n.__( 'Enter tweet URL to embed...' ) }
+							onChange={ ( event ) => this.setState( { url: event.target.value } ) } />
+						{ ! fetching ?
+							(
+								<Button
+									isLarge
+									type="submit">
+									{ wp.i18n.__( 'Embed' ) }
+								</Button>
+							) : (
+								<span className="spinner is-active" />
+							)
+						}
+					</form>
+					{ error && ( <p className="components-placeholder__error">{ wp.i18n.__( 'Sorry, we couldn\'t fetch that tweet.' ) }</p> ) }
+				</Placeholder>
+			);
+		}
+	},
+
+	save( { attributes } ) {
+		const { url } = attributes;
+		return url;
+	}
+} );
diff --git a/components/placeholder/style.scss b/components/placeholder/style.scss
index d28fea95f215cc..e6414ea3bccfa8 100644
--- a/components/placeholder/style.scss
+++ b/components/placeholder/style.scss
@@ -25,9 +25,15 @@
 .components-placeholder__fieldset {
 	display: flex;
 	flex-direction: row;
+	flex-wrap: wrap;
 	justify-content: center;
 	width: 100%;
 	max-width: 280px;
+
+	.components-placeholder__error {
+		font-family: $default-font;
+		font-size: $default-font-size;
+	}
 }
 
 .components-placeholder__input {
diff --git a/components/resizable-iframe/README.md b/components/resizable-iframe/README.md
new file mode 100644
index 00000000000000..b6423601d7a566
--- /dev/null
+++ b/components/resizable-iframe/README.md
@@ -0,0 +1,46 @@
+Resizable Iframe
+================
+
+Resizable Iframe is a React component for rendering an `<iframe>` element which can dynamically update its own dimensions using [`window.postMessage`](https://developer.mozilla.org/en-US/docs/Web/API/Window.postMessage). This is useful in cases where an inline frame of an unknown size is to be displayed on the page.
+
+## Example
+
+The `ResizableIframe` component can be used in much the same way that you would use an `<iframe>` DOM element. Props are automatically transferred to the rendered `<iframe>`, in case you need to specify additional properties or styles.
+
+```html
+<ResizableIframe src={ myFrameUrl } frameBorder={ 0 } />
+```
+
+## Usage
+
+To allow for resizing of the element, a `ResizableIframe` element listens for `message` events on the `window` object. If the rendered frame is not sandboxed, a script is injected in the frame to manage this behavior on your behalf. If the frame is sandboxed, any page you reference as the `src` URL is responsible for invoking this event using [`window.postMessage`](https://developer.mozilla.org/en-US/docs/Web/API/Window.postMessage). The message should be a JSON string with an `action` value of "resize" and a numeric `width` and `height` to define the new pixel dimensions of the element.
+
+For example, a page can trigger a resize using the following code snippet:
+
+```javascript
+if ( window.parent ) {
+	window.parent.postMessage( JSON.stringify( {
+		action: 'resize',
+		width: document.body.clientWidth,
+		height: document.body.clientHeight
+	} ), '*' );
+}
+```
+
+## Props
+
+### `src`
+
+Treated as the `src` URL to be used in the rendered `<iframe>` DOM element.
+
+### `width`
+
+An optional fixed width value, if you don't want this to be the responsibility of the child window.
+
+### `height`
+
+An optional fixed height value, if you don't want this to be the responsibility of the child window.
+
+### `onResize`
+
+An optional function to trigger when the rendered frame has been resized.
diff --git a/components/resizable-iframe/index.js b/components/resizable-iframe/index.js
new file mode 100644
index 00000000000000..095a02748e4fd5
--- /dev/null
+++ b/components/resizable-iframe/index.js
@@ -0,0 +1,171 @@
+/**
+ * Imported from Calypso, with some lint fixes and gutenburg specific changes.
+ */
+
+/**
+ * External dependencies
+ */
+import { omit } from 'lodash';
+
+export default class ResizableIframe extends wp.element.Component {
+
+	constructor() {
+		super( ...arguments );
+		this.state = {
+			width: 0,
+			height: 0
+		};
+		this.getFrameBody = this.getFrameBody.bind( this );
+		this.maybeConnect = this.maybeConnect.bind( this );
+		this.isFrameAccessible = this.isFrameAccessible.bind( this );
+		this.checkMessageForResize = this.checkMessageForResize.bind( this );
+	}
+
+	static get defaultProps() {
+		return {
+			onLoad: () => {},
+			onResize: () => {},
+			title: ''
+		};
+	}
+
+	componentDidMount() {
+		window.addEventListener( 'message', this.checkMessageForResize, false );
+		this.maybeConnect();
+	}
+
+	componentDidUpdate() {
+		this.maybeConnect();
+	}
+
+	componentWillUnmount() {
+		window.removeEventListener( 'message', this.checkMessageForResize );
+	}
+
+	getFrameBody() {
+		return this.iframe.contentDocument.body;
+	}
+
+	maybeConnect() {
+		if ( ! this.isFrameAccessible() ) {
+			return;
+		}
+
+		const body = this.getFrameBody();
+		if ( null !== body.getAttribute( 'data-resizable-iframe-connected' ) ) {
+			return;
+		}
+
+		const script = document.createElement( 'script' );
+		script.innerHTML = `
+			( function() {
+				var observer;
+
+				if ( ! window.MutationObserver || ! document.body || ! window.top ) {
+					return;
+				}
+
+				function sendResize() {
+					window.top.postMessage( {
+						action: 'resize',
+						width: document.body.offsetWidth,
+						height: document.body.offsetHeight
+					}, '*' );
+				}
+
+				observer = new MutationObserver( sendResize );
+				observer.observe( document.body, {
+					attributes: true,
+					attributeOldValue: false,
+					characterData: true,
+					characterDataOldValue: false,
+					childList: true,
+					subtree: true
+				} );
+
+				window.addEventListener( 'load', sendResize, true );
+
+				// Hack: Remove viewport unit styles, as these are relative
+				// the iframe root and interfere with our mechanism for
+				// determining the unconstrained page bounds.
+				function removeViewportStyles( ruleOrNode ) {
+					[ 'width', 'height', 'minHeight', 'maxHeight' ].forEach( function( style ) {
+						if ( /^\\d+(vmin|vmax|vh|vw)$/.test( ruleOrNode.style[ style ] ) ) {
+							ruleOrNode.style[ style ] = '';
+						}
+					} );
+				}
+
+				Array.prototype.forEach.call( document.querySelectorAll( '[style]' ), removeViewportStyles );
+				Array.prototype.forEach.call( document.styleSheets, function( stylesheet ) {
+					Array.prototype.forEach.call( stylesheet.cssRules || stylesheet.rules, removeViewportStyles );
+				} );
+
+				document.body.style.position = 'absolute';
+				document.body.setAttribute( 'data-resizable-iframe-connected', '' );
+
+				sendResize();
+			} )();
+		`;
+		body.appendChild( script );
+	}
+
+	isFrameAccessible() {
+		try {
+			return !! this.getFrameBody();
+		} catch ( e ) {
+			return false;
+		}
+	}
+
+	checkMessageForResize( event ) {
+		const iframe = this.iframe;
+
+		// Attempt to parse the message data as JSON if passed as string
+		let data = event.data || {};
+		if ( 'string' === typeof data ) {
+			try {
+				data = JSON.parse( data );
+			} catch ( e ) {} // eslint-disable-line no-empty
+		}
+
+		// Verify that the mounted element is the source of the message
+		if ( ! iframe || iframe.contentWindow !== event.source ) {
+			return;
+		}
+
+		// Update the state only if the message is formatted as we expect, i.e.
+		// as an object with a 'resize' action, width, and height
+		const { action, width, height } = data;
+		const { width: oldWidth, height: oldHeight } = this.state;
+
+		if ( 'resize' === action && ( oldWidth !== width || oldHeight !== height ) ) {
+			this.setState( { width, height } );
+			this.props.onResize();
+		}
+	}
+
+	onLoad( event ) {
+		this.maybeConnect();
+		this.props.onLoad( event );
+	}
+
+	render() {
+		const omitProps = [ 'onResize' ];
+
+		if ( ! this.props.src ) {
+			omitProps.push( 'src' );
+		}
+		return (
+			<iframe
+				ref={ ( node ) => this.iframe = node }
+				title={ this.props.title }
+				seamless="seamless"
+				scrolling="no"
+				{ ...omit( this.props, omitProps ) }
+				onLoad={ this.onLoad }
+				width={ this.props.width || this.state.width }
+				height={ this.props.height || this.state.height } />
+		);
+	}
+}
diff --git a/components/sandbox/index.js b/components/sandbox/index.js
new file mode 100644
index 00000000000000..db0b68e9787c44
--- /dev/null
+++ b/components/sandbox/index.js
@@ -0,0 +1,46 @@
+/**
+ * Internal dependencies
+ */
+import ResizableIframe from 'components/resizable-iframe';
+
+export default class Sandbox extends wp.element.Component {
+
+	static get defaultProps() {
+		return {
+			html: '',
+			title: '',
+		};
+	}
+
+	componentDidMount() {
+		const body = this.node.getFrameBody();
+		const { html } = this.props;
+
+		body.innerHTML = html;
+
+		// setting the inner HTML will not cause scripts to load,
+		// so this prepares a bunch of new script elements and
+		// appends them to the iframe's body
+		const scripts = body.getElementsByTagName( 'script' );
+		const newscripts = [];
+
+		for ( let i = 0; i < scripts.length; i++ ) {
+			const newscript = document.createElement( 'script' );
+			newscript.src = scripts[ i ].src;
+			newscripts.push( newscript );
+		}
+
+		for ( let i = 0; i < newscripts.length; i++ ) {
+			body.appendChild( newscripts[ i ] );
+		}
+	}
+
+	render() {
+		return (
+			<ResizableIframe
+				sandbox="allow-same-origin allow-scripts"
+				title={ this.props.title }
+				ref={ ( node ) => this.node = node } />
+		);
+	}
+}
diff --git a/package.json b/package.json
index f9d5cf293845d4..3ecb60e1f3ee38 100644
--- a/package.json
+++ b/package.json
@@ -53,6 +53,7 @@
     "extract-text-webpack-plugin": "^2.1.0",
     "gettext-parser": "^1.2.2",
     "glob": "^7.1.1",
+    "jquery": "^3.2.1",
     "jsdom": "^9.12.0",
     "mocha": "^3.2.0",
     "node-sass": "^4.5.0",
diff --git a/post-content.js b/post-content.js
index b5acb20997765d..057c9d1c7db72b 100644
--- a/post-content.js
+++ b/post-content.js
@@ -128,6 +128,14 @@ window._wpGutenbergPost = {
 			'<!-- wp:core/list -->',
 			'<ul><li>Est quis reque cetero ad</li><li>Sea id autem nominavi deseruisse</li><li>Veniam qualisque definitionem pri id, ea autem feugiat delenit ius, mei at loem affert accumsan</li><li>Dicat eruditi cu est, te pro dicant pericula conclusionemque</li><li>Eius postea volumus mei ad</li></ul>',
 			'<!-- /wp:core/list -->',
+
+			'<!-- wp:core/embed url="https://www.youtube.com/watch?v=Nl6U7UotA-M" -->',
+			'<iframe width="560" height="315" src="//www.youtube.com/embed/Nl6U7UotA-M" frameborder="0" allowfullscreen></iframe>',
+			'<!-- /wp:core/embed -->',
+
+			'<!-- wp:core/tweet -->',
+			'https://twitter.com/automattic/status/777261837335326720',
+			'<!-- /wp:core/tweet -->',
 		].join( '' ),
 	},
 };
diff --git a/webpack.config.js b/webpack.config.js
index 80654973dbf514..0a9968259b7f14 100644
--- a/webpack.config.js
+++ b/webpack.config.js
@@ -23,6 +23,7 @@ const config = {
 		react: 'React',
 		'react-dom': 'ReactDOM',
 		'react-dom/server': 'ReactDOMServer',
+		jquery: 'jQuery',
 		tinymce: 'tinymce'
 	},
 	resolve: {