JSFiddle - React, Tailwind, and code Playground

HTML

<div class="px500">500px</div>
<div class="rem50">50rem</div>

CSS

html {
  font-size: 10px; /* override `rem` */
}

div {
  background: red;
  height: 100px;
  width: 100px;
}

@media screen and ( max-width: 500px ) {
  .px500 {
    background: green;
  }
}

@media screen and ( max-width: 50rem ) {
  .rem50 {
    background: green;
  }
}