JSFiddle - React, Tailwind, and code Playground

HTML

<div class="outer">
  <div class="inner1">
    inner1
  </div>
  <div class="inner2">
    inner2
  </div>
</div>

CSS

div.outer {
  background-color: gray;
  padding: 0 10px 0 10px;
}
div.inner1 {
  width: 100%;
  background-color: green;
}
div.inner2 {
  width: auto;
  background-color: blue;
}