JSFiddle - React, Tailwind, and code Playground

HTML

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

CSS

#outer{
  width:500px;
  background-color:#000;
  height:500px
}
#inner{
  background-color:#333;
  margin:0 auto;
  width:50%;
  height:250px;
}