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