JSFiddle - React, Tailwind, and code Playground

HTML

<div>

</div>

CSS

@keyframes taille {
    0% {width: 100px;}
    50% {width: 200px;}
    100% {width: 100px;}
}

div {
    height: 100px;
    width: 100px;
    background-color: blue;
    animation-name: taille;
    animation-duration: 4s;
}