JSFiddle - React, Tailwind, and code Playground

HTML

<div id="something1">
  <div id="something2"></div>
  <div id="parent">
    <div id="child"></div>
  </div>
</div>

CSS

#parent {
    border: 5px solid gray;
    position: relative;
    height: 100px;
    width: 100px;
    margin-left: 50px;
}

#child {
    position: absolute;
    top:0;
    left: 0;
    right: 0;
    bottom: 0;
    background: red;
}

#something2 {
    border: 5px solid blue;
    height: 100px;
    width: 100px;
}