Best Optical Illusions

It's been a while since I've shared some more optical illusions with you.
Here are some of the best illusions according to Scientific American.

I'll leave you with just one. What do you see in the following image?

If you see an embraced couple, you should give it a closer look until you see the dolphins. :)

Apparentely children see the dolphins first, while "sexual" grown-ups focus on the nude bodies first.


But, if that's not ebought, check out these upward rolling slopes.