JSFiddle - React, Tailwind, and code Playground

HTML

<div class="parent">
  <div class="first">
     Hello
  </div>
  <div class="second" >
  </div>
</div>

CSS

.parent {
  height: 500px;
  min-width: 500px;
  position: relative;
  background-color: red;
}

.first {
  background-color: green;
  margin-bottom: 10px;
}

.second {
  height: 100px;
  background-color: grey;
  bottom: 0px;
  box-sizing: border-box;
  position: absolute;
  width: 100%;
}