JSFiddle - React, Tailwind, and code Playground

HTML

<div id="foo"></div>

CSS

#foo:after {
    content: '';
    width: 200px;
    height: 200px;
    background: red;
    display: block;
    -webkit-transition: all 1s ease-in-out;
    -moz-transition: all 1s ease-in-out;
    -o-transition: all 1s ease-in-out;
}

#foo:hover:after {
    width: 250px;
    height: 250px;
}