JSFiddle - React, Tailwind, and code Playground

HTML

<div class="pixel">
 Some text here
</div>

<div class="em">
  Some text here
</div>

CSS

.pixel {
  background-color: lightblue;
  width: 160px;
  font-size: 16px;
}

.em {
  background-color: green;
  font-size: 1em;
  width: 10em;
}