JSFiddle - React, Tailwind, and code Playground

HTML

<div id="outer">
  <div id="inner"></div>
</div>

CSS

html, body {
  height:100%;
  margin:0;
  width:100%;
}

#outer {
  background:red;
  height:50%;
  padding:20px;
  position:absolute;
  width:50%;
}

#inner {
  background:yellow;
  height:100%;
  position:absolute;
  width:100%;
}