JSFiddle - React, Tailwind, and code Playground

HTML

<div id="wrapper">
        <div id="one">100% height & width, all you can see when opening this file!</div>
        <div id="two">I'll be 100% when you've scrolled #1 out of the window!</div>
    </div>

CSS

* {
  margin:0;
  padding:0;
}
html, body {
   height:100%;
}
#wrapper, #one, #two {
   width:100%;
   height:100%;
}
#one {background:orange;}
#two {background:pink;}