JSFiddle - React, Tailwind, and code Playground

HTML

<div id='parent'>
    
    <div id='child'></div>
</div>

CSS

#parent {
    width: 200px;
    height: 200px;
    background: blue;
}
#child {
    display: none;
    width: 100px;
    height: 100px;
    background: red;
}
#parent:hover #child {
    display: block;
}