SOURCE

<section>
  <div class="float">Try to resize this outer float</div>
  <div class="box"><p>Normafwepktgperkgopkerthopkgel</p></div>
</section>

section{
	border:10px solid purple;
  
  .float{
    border:10px solid black;
    float:left;
    width: 50%;
    box-sizing: border-box;
  }
  .box{
    border:3px solid blue;
    box-sizing: border-box;
    /* display: flow-root; */
  }
}