These boxes both have a height set, this box has content in it which will need more space than the assigned height, and so we get overflow.
.box { border: 5px solid darkblue; height: 150px; width: 200px; }
<div class="wrapper"> <div class="box"></div> <div class="box">These boxes both have a height set, this box has content in it which will need more space than the assigned height, and so we get overflow. </div> </div>