Say I have:
<div class="thing">
<a>hi</a>
<span class="poo">
<p id="hello">my name is</p>
</span>
</div>
<div class="thing">
<a>hi</a>
<span class="poo">
nothing to see here
</span>
</div>
I want to select the first div, but only because it has a p#hello
inside it.