It's an old picture, but its intrigue and frustration never gets old. What animal do you see when you look at this?

Did you see a frog? You're not alone.

But it's the rare eye that picks up the other animal - a horse. Can you spot it?

No? Here's a hint. Look at the space between the frog's legs. There's a strange hollow space there.

And if you're still not spotting, let's turn it sideways.

And here's the eye and nostril.

Did you see it?! Well, here it is for those of us who need to see it in outline.

Optical illusions are so cool! Did you spot the horse before it was pointed out?