How to make div break line?

Question

I have the following code:

.thing {
  width: 90%;
  height: 400px;
  border: 10px solid #000;
}

<div class="thing">
  aaaaaaaaaaaa
</div>

The problem is that when I add to much content, the text goes out of the div!

How to fix this using only CSS?

Answer 1

.thing {
width: 90%;
height: 400px;
padding: 10px solid #000;
word-break:break-all;
}

use word-break