I have the following code:

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

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

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

[![](https://i.imgur.com/Xa51x2J.png)](https://i.imgur.com/Xa51x2J.png)

How to fix this using only CSS?