<body>
  <div>
    I am 10px
    <div>
      I am 20px
      <div>
        I am 4px
        <div>
          I am 80px
            <div>My parent is my base size, so because my parent is having 80px font size which is 1em so my font size is now 160px for 2em</div>
        </div>
      </div>
    </div>
  </div>
</body>
body { font-size:5px; } 
div { font-size:2em; }
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