diff --git a/package.json b/package.json
index 5fd7dcc..b69f8d3 100644
--- a/package.json
+++ b/package.json
@@ -14,7 +14,7 @@
     "serve": "webpack-dev-server --host 0.0.0.0 --hot --inline --history-api-fallback",
     "start": "npm-run-all --parallel karma:dev serve",
     "karma:once": "karma start --single-run",
-    "karma:dev": "karma start --browsers Chrome",
+    "karma:dev": "karma start --browsers Chromium",
     "babel": "babel src -d lib",
     "build": "npm-run-all clean babel",
     "lint": "eslint '*.js' '{src,test}/**/*.js*'",
diff --git a/src/Content.jsx b/src/Content.jsx
index 2b4262b..bc17267 100644
--- a/src/Content.jsx
+++ b/src/Content.jsx
@@ -5,7 +5,8 @@ export default class Content extends Component {
   static propTypes = {
     children: PropTypes.element.isRequired,
     contentDidMount: PropTypes.func.isRequired,
-    contentDidUpdate: PropTypes.func.isRequired
+    contentDidUpdate: PropTypes.func.isRequired,
+    contentWillUnmount: PropTypes.func.isRequired
   };
 
   componentDidMount() {
@@ -16,6 +17,10 @@ export default class Content extends Component {
     this.props.contentDidUpdate();
   }
 
+  componentWillUnmount() {
+    this.props.contentWillUnmount();
+  }
+
   render() {
     return Children.only(this.props.children);
   }
diff --git a/src/Frame.jsx b/src/Frame.jsx
index 767362a..9498fad 100644
--- a/src/Frame.jsx
+++ b/src/Frame.jsx
@@ -16,6 +16,7 @@ export class Frame extends Component {
     mountTarget: PropTypes.string,
     contentDidMount: PropTypes.func,
     contentDidUpdate: PropTypes.func,
+    contentWillUnmount: PropTypes.func,
     children: PropTypes.oneOfType([
       PropTypes.element,
       PropTypes.arrayOf(PropTypes.element)
@@ -29,6 +30,7 @@ export class Frame extends Component {
     mountTarget: undefined,
     contentDidMount: () => {},
     contentDidUpdate: () => {},
+    contentWillUnmount: () => {},
     initialContent:
       '<!DOCTYPE html><html><head></head><body><div class="frame-root"></div></body></html>'
   };
@@ -97,12 +99,14 @@ export class Frame extends Component {
 
     const contentDidMount = this.props.contentDidMount;
     const contentDidUpdate = this.props.contentDidUpdate;
+    const contentWillUnmount = this.props.contentWillUnmount;
 
     const win = doc.defaultView || doc.parentView;
     const contents = (
       <Content
         contentDidMount={contentDidMount}
         contentDidUpdate={contentDidUpdate}
+        contentWillUnmount={contentWillUnmount}
       >
         <FrameContextProvider value={{ document: doc, window: win }}>
           <div className="frame-content">{this.props.children}</div>
@@ -129,6 +133,7 @@ export class Frame extends Component {
     delete props.mountTarget;
     delete props.contentDidMount;
     delete props.contentDidUpdate;
+    delete props.contentWillUnmount;
     delete props.forwardedRef;
     return (
       <iframe {...props} ref={this.setRef} onLoad={this.handleLoad}>
diff --git a/test/Content.spec.jsx b/test/Content.spec.jsx
index b48c290..2892f85 100644
--- a/test/Content.spec.jsx
+++ b/test/Content.spec.jsx
@@ -1,19 +1,33 @@
 import React from 'react';
+import ReactDOM, { unmountComponentAtNode } from 'react-dom';
 import ReactTestUtils from 'react-dom/test-utils';
 import { expect } from 'chai';
 import sinon from 'sinon/pkg/sinon';
 import Content from '../src/Content';
 
 describe('The Content component', () => {
+  let div;
+
+  afterEach(() => {
+    if (div) {
+      div.remove();
+      div = null;
+    }
+  });
+
   it('should render children', () => {
     const content = ReactTestUtils.renderIntoDocument(
-      <Content contentDidMount={() => null} contentDidUpdate={() => null}>
+      <Content
+        contentDidMount={() => null}
+        contentDidUpdate={() => null}
+        contentWillUnmount={() => null}
+      >
         <div className="test-class-1" />
       </Content>
     );
 
-    const div = ReactTestUtils.findRenderedDOMComponentWithTag(content, 'div');
-    expect(div.className).to.equal('test-class-1');
+    const elem = ReactTestUtils.findRenderedDOMComponentWithTag(content, 'div');
+    expect(elem.className).to.equal('test-class-1');
   });
 
   it('should call contentDidMount on initial render', () => {
@@ -30,7 +44,7 @@ describe('The Content component', () => {
     expect(didUpdate.callCount).to.equal(0);
   });
 
-  it('should call contentDidUpdate on subsequent updates', (done) => {
+  it('should call contentDidUpdate on subsequent updates', done => {
     const didMount = sinon.spy();
     const didUpdate = sinon.spy();
 
@@ -54,4 +68,49 @@ describe('The Content component', () => {
       });
     });
   });
+
+  it('should call contentWillUnmount before unmounting', done => {
+    div = document.body.appendChild(document.createElement('div'));
+    const didMount = sinon.spy();
+    const didUpdate = sinon.spy();
+    const willUnmount = sinon.spy();
+
+    const Parent = () => (
+      <Content
+        contentDidMount={didMount}
+        contentDidUpdate={didUpdate}
+        contentWillUnmount={willUnmount}
+      >
+        <div className="test-class-1" />
+      </Content>
+    );
+
+    ReactDOM.render(<Parent />, div);
+
+    expect(didMount.callCount).to.equal(1);
+    expect(didUpdate.callCount).to.equal(0);
+    unmountComponentAtNode(div);
+    expect(willUnmount.callCount).to.equal(1);
+    done();
+  });
+
+  it('should error if null is passed in contentWillUnmount', () => {
+    ReactTestUtils.renderIntoDocument(
+      <Content
+        contentDidMount={() => null}
+        contentDidUpdate={() => null}
+        contentWillUnmount={null}
+      >
+        <div className="test-class-1" />
+      </Content>
+    );
+  });
+
+  it('should not error if contentWillUnmount is not passed as a prop', () => {
+    ReactTestUtils.renderIntoDocument(
+      <Content contentDidMount={() => null} contentDidUpdate={() => null}>
+        <div className="test-class-1" />
+      </Content>
+    );
+  });
 });
diff --git a/test/Frame.spec.jsx b/test/Frame.spec.jsx
index c90242b..9ceca5c 100644
--- a/test/Frame.spec.jsx
+++ b/test/Frame.spec.jsx
@@ -1,6 +1,6 @@
 import React from 'react';
 import PropTypes from 'prop-types';
-import ReactDOM from 'react-dom';
+import ReactDOM, { unmountComponentAtNode } from 'react-dom';
 import ReactTestUtils from 'react-dom/test-utils';
 import { expect } from 'chai';
 import sinon from 'sinon/pkg/sinon';
@@ -313,6 +313,55 @@ describe('The Frame Component', () => {
     );
   });
 
+  it('should call contentWillUnmount on unmount', done => {
+    div = document.body.appendChild(document.createElement('div'));
+    const willUnmount = sinon.spy();
+
+    const Thing = () => (
+      <Frame contentWillUnmount={willUnmount}>
+        <div className="test-class-1" />
+      </Frame>
+    );
+
+    ReactDOM.render(<Thing />, div);
+
+    // TODO: act() doesn'tt seem to solve this something weird???
+    setTimeout(() => {
+      unmountComponentAtNode(div);
+      expect(willUnmount.callCount).to.equal(1, 'expected 1 willUnmount');
+      done();
+    }, 100);
+  });
+
+  it('should error when null is passed in contentWillUnmount', () => {
+    div = document.body.appendChild(document.createElement('div'));
+    ReactDOM.render(<Frame contentWillUnmount={null} />, div);
+  });
+
+  it('should not error when contentWillUnmount is not passed', done => {
+    div = document.body.appendChild(document.createElement('div'));
+    const didUpdate = sinon.spy();
+    const didMount = sinon.spy();
+    const frame = ReactDOM.render(
+      <Frame
+        contentDidUpdate={didUpdate}
+        contentDidMount={() => {
+          didMount();
+          frame.setState({ foo: 'bar' }, () => {
+            expect(didMount.callCount).to.equal(1, 'expected 1 didMount');
+            expect(didUpdate.callCount).to.equal(1, 'expected 1 didUpdate');
+            frame.setState({ foo: 'gah' }, () => {
+              expect(didMount.callCount).to.equal(1, 'expected 1 didMount');
+              expect(didUpdate.callCount).to.equal(2, 'expected 2 didUpdate');
+              done();
+            });
+          });
+        }}
+      />,
+      div
+    );
+  });
+
   it('should return first child element of the `body` on call to `this.getMountTarget()` if `props.mountTarget` was not passed in', () => {
     div = document.body.appendChild(document.createElement('div'));
 
