Looks like a star. Now zoom in...

There's a tiny patch of sky known as the Groth Strip that looks like this:

(Ignore the arrow added on to the image)

It's that tiny strip up near the top and slightly to the left. Someone the other day directed me to this page, showing all the stars in this tiny strip of sky. Except that most of them aren't stars...the image is zoomable so you can see exactly what they're made of. The strip looks like this:

But if we zoom in to a part of this (a tiny part of that tiny part of the sky) we can see that most of the tiniest pixels are actually galaxies, so instead of one star we're looking at a few hundred billion of them.

There are more images of this type here. Another great one is this one, the galaxy M101. Zooming in suddenly and then waiting a few seconds while the image buffers and becomes clearer and clearer is great fun. I just wish I could keep zooming in.