Why is the parent div's clientHeight smaller than its child's clientHeight? _html/css_WEB-ITnose

How can I make the height of the parent div increase as the height of the child div increases?
Such as

partition 1 has a height of 100px. The height of partition 2 is 200px. How is this result caused?

Reply to discussion (solution)

Use float, clear float

Use float Well, clear float

Well, I used it, and it was indeed caused by it. If I don’t use it, how can I make the two divs line up?

Reference

<div style="background:red;">  <div style="display:inline-block;">aaaaaa</div><div  style="display:inline-block;">cccc<br>bbbbb</div>  </div>  <br><div style="background:red;">  <div>aaaaaa</div><div  style="float:right;">cccc<br>bbbbb</div> <div style="clear:both;"></div> </div>

Use float, clear float

Well, I used it, it turned out to be it Caused by this, if you don't use it, how can you make the two divs line up?