JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
   <div id="test"></div>
</div>

CSS

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

#container {
  background: red;
  width: 100%;
  height: 100%;
}

#test {
  background: blue;
  width: 50%;
  height: 50%;
}