JSFiddle - React, Tailwind, and code Playground

HTML

<div id="div">привет</div>
<p id="poka">пока</p>

CSS

p, #div {
    background-color: #333;
    margin: 5px;
}
#div + p {
    display: block;
    -webkit-transition: opacity 1s ease-out;
    transition: opacity 1s ease-out;
    opacity: 0; 
    height: 0;
    overflow: hidden;
}

#div:hover + p {
    opacity: 1;
    height: auto;
}