<!DOCTYPE html>
<!--
 | Unitless line height uses the font size of the element where it is used, not
 | the font size of the element where it is declared.
 |   https://www.w3.org/TR/CSS2/visudet.html#line-height
 -->
<html>
 <head>
 <style>
  body { margin: 0px; font-family: Roboto; }
  span { background-color: #009688;  }
 </style>
 </head>
 <body>
  <div style="width:50px; background-color: #80CBC4">
   <span style="font-size: 10px; line-height: 2">
    xxxxxxx xxxxxxx
    xxx<span style="font-size: 20px">xx xxxx</span>
    xxx<span style="line-height: 5">xxx</span>
   </span>
  </div>
 </body>
</html>