JSFiddle - React, Tailwind, and code Playground

HTML

<div id="div1">

</div>
<br>
<div id="div2">

</div>

CSS

div {
  position: relative;
  float: left;
}

#div1 {
  background-color: cyan;
  width: 200px;
  height: 100px;
  padding-bottom:30px;
}

#div2 {
  background-color: lime;
  width: 400px;
  height: 50px;
}

div:after {
  content: "";
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  box-shadow: 0 0 12px black;
  z-index: -1;
}