<!DOCTYPE HTML> <style> div.outer { font-size: 12px; width: 600px } div.middle { width: 450px; } div.inner { width: 300px; } </style> <!-- In a 450px container, the minimum font size at 15em per line is 30px. This means we map 0px-45px into 30px-45px, so 12px gets mapped to 34px. --> <div class="outer"> <div class="middle"> Text in middle. <div class="inner">Text in inner.</div> </div> </div>