JSFiddle - React, Tailwind, and code Playground

HTML

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

CSS

#container {
    width: 100px;
    height: 100px;
    overflow:hidden;
    background-color: red;
}
#inner {
    
    margin:30px;    
    width: 40px;
    height: 40px;
    background-color: black;
}