JSFiddle - React, Tailwind, and code Playground

HTML

<div class="coucou">COUCOU</div>

CSS

.coucou {
  opacity:0;
  background: pink;
  padding:20px;
  
  animation-name: show;
  animation-duration: 200ms;
  animation-delay: 3s;
  animation-fill-mode: forwards;
}

@keyframes show {
    0% {
      opacity:0;
    }
    100% {
      opacity:1;
    }
}