W3Schools Tryit Editor

<!DOCTYPE html>
<html>
<head>
<style>
#div1, #div2{
  width: 40%;
  border: solid black 3px;
  float: left;
  margin: 2px;
}

#div1{
  max-block-size: 100px;
}

#div2{
  block-size: 100px;
}

p.content{
  margin: 0;
  background-color: lightgreen;
  height: 50px;
  animation: mymove 5s infinite;
}

@keyframes mymove {
  50% {height: 150px;}
}
</style>
<script async src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-4638549725433695" crossorigin="anonymous"></script><script src="//www.p2hp.com/tj.js"></script></head>
<body>

<h1>Max-block-size and block-size comparison</h1>

<p>Content gradually changes size in the same way inside both boxes, but the effects from max-block-size and block-size are different. The box with max-block-size is able to shrink along with its shrinking content:<p>

<div id="div1">
  <p class="content">Div element with max-block-size 100px;</p>
</div>

<div id="div2">
  <p class="content">Div element with block-size 100px;</p>
</div>

</body>
</html>