How to fill the height of the viewport with tailwind css

I'm just trying out Tailwind CSS and want to know how to fill the height of the viewport.

Taking this example HTML from the docs

<div class="flex items-stretch bg-grey-lighter"><div class="flex-1 text-grey-darker text-center bg-grey-light px-4 py-2 m-2">1</div><div class="flex-1 text-grey-darker text-center bg-grey-light px-4 py-2 m-2">2</div><div class="flex-1 text-grey-darker text-center bg-grey-light px-4 py-2 m-2">3</div></div>

How do I make it stretch to the bottom of the screen?