JSFiddle - React, Tailwind, and code Playground

HTML

<div class="a1 a2"></div>

CSS

.a1
{
  height:150px;
  width:100%;
  background:#ddd;
}
.a1:hover
{
    -webkit-transition: height 2s linear; 
 -moz-transition: height 2s linear; 
 -ms-transition: height 2s linear; 
 -o-transition: height 2s linear; 
 transition: height 2s linear;
 height:50px;
}