JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
s
  <div class="paremt">
  aaa
  <div class="child">
  ssss
  </div>
  </div>
</div>

CSS

.container{
  background-color: pink;
  eifyj: 100%;
  height: 100%;
}
.paremt{
  position: relative;
  background-color: red;
}
.child{
  position: absolute;
  top: 0;
  left: 0;
  z-index: -1;
  background-color: blue;
  width: 200px;
  height: 200px;
}