JSFiddle - React, Tailwind, and code Playground

HTML

<h1>CSS IS AWESOME</h1>

CSS

h1 {
	color: #666;	
}

h1:after {
	position: absolute;
	left: 10px;
	content: '';
	height: 40px;
	width: 275px; 
	border-bottom: solid 3px #019fb6;
	transition: all 1000ms ease-in-out;	
	opacity: 0;
}

h1:hover:after {
	opacity: 1;
}