JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8/themes/dot-luv/jquery-ui.css">
<div id='parent'>
   <div id='over' style='position: absolute; width: 100px; height: 100px'></div>
   <div id='under' style='width: 100px; height: 100px'></div>
</div>

CSS

#over { background: red; }
#under { background: green; }