JSFiddle - React, Tailwind, and code Playground

HTML

<div id="hover">Hover here</div>
<div id="stuff">Look stuff
    <br/>
    
</div>

CSS

#stuff {
    opacity: 0.0;
    -webkit-transition: all 500ms ease-in-out;
    -moz-transition: all 500ms ease-in-out;
    -ms-transition: all 500ms ease-in-out;
    -o-transition: all 500ms ease-in-out;
    transition: all 500ms ease-in-out;
}

#hover:hover + #stuff {
    opacity: 1.0;
}