JSFiddle - React, Tailwind, and code Playground

HTML

<p></p>
<div></div>

CSS

p{
  height:10px;
  background: black;
}
div{
  display:none;
  background:red;
  height:0px;
  transition:all 1s;
}
p:hover+div{
  display:block;
  height:200px;
}