JSFiddle - React, Tailwind, and code Playground

HTML

<!-- div1 div2 -->
<div class="wrapper">
  <div class="div1">div1</div>
  <div class="div2">div2</div>
</div>

CSS

/* div1 div2 */

.wrapper {
  position: relative;
  width: 100%;
  height: 200px;
}

.div1,
.div2 {
  position: absolute;
  left: 0;
  top: 0;
  right: auto;
  bottom: auto;
  width: 100%;
  height: 100%;
}

.div1 {
  background: green;
  z-index: 10;
  
}
.div2 {
  with: 90%;
}

.div2 {
  background: blue;
  z-index: 20;
}

JavaScript

/* div1 div2 */