JSFiddle - React, Tailwind, and code Playground

HTML

<div class="first">Один блок<div class="second">Два блок</div></div>

CSS

.first{
    background: #f00;
    padding: 10px;
}

.second{
    background: yellow;
    padding: 10px;
    display: none;
}

.first:hover .second{
    display: block;
}