JSFiddle - React, Tailwind, and code Playground

HTML

<div>
    <span></span>
</div>

CSS

div {
    height: 100px;
    width: 100px;
    background: #f00;
    margin: 100px;
}

div span {
    display: none;
}

div:hover span {
    height: 20px;
    width: 100%;
    position: absolute;
    background: #0f0;
    bottom: 0;
    display: block;
}