JSFiddle - React, Tailwind, and code Playground

HTML

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

CSS

#outer {
    position: relative;
    width: 200px;
    height: 200px;
    background: #ccc;
}
#inner {
    width: 50px;
    height: 50px;
    background: #f00;
    position: absolute;
    top: 0;
}