How do I get a wrapper div that is 100% height to expand its with the height of its children? That are also 100% in height.

The setup looks like this:

```
<div id="wrapper" style="height:100%">
  <div class="child" style="height:100%">div1</div>
  <div class="child" style="height:100%">div2</div>
</div>

```

But the wrapper dosen't expand to 200% height. I have tried making the wrapper `min-height:100%;` but then the children don't inherit the full height, only the height of their own content. 

<https://jsfiddle.net/on78pof8/>

(The aqua colored box, dosen't expand)