JSFiddle - React, Tailwind, and code Playground

HTML

<div class="relative"><div class="relative"></div></div>

CSS

body {
  position: absolute;
  height: 100%;
  width: 100%;
}
.relative
{
  position: relative;
  display: block;
  height: 60%;
  width: 75%;
  background: #000;
}
.relative .relative {
background: green}