JSFiddle - React, Tailwind, and code Playground

HTML

<div class="parent">

  Hello Parent!

  <div class="child">
    Hello Child!
  </div>

</div>

SCSS

.parent { 

  font-size: 1em;
  
  .child {
    font-size: 0.8em;
  }
  
  // Extra small devices (portrait phones, less than 576px)
  @media (max-width: 575px) {
    font-size: 0.8em;
  }

}