> `null` and `false` can also be used as return values. This is a nice shorthand to indicate you don't want anything rendered into the DOM. Behind the scenes, React renders a `<script>` tag to work with our current node tracking. When returning `null` or `false`, `this.getDOMNode()` will return null.

Or something like that. I wouldn't mention `undefined`. Might also want to add the null note to `getDOMNode()`