New Delhi, May 31 -- Optical illusions are images or scenes that trick the eyes and brain into seeing something that isn't immediately obvious. They're not just fun-they also help us understand how human perception works and can even train the brain to focus better.

One such clever illusion is going viral for all the right reasons. A tiny picnic table filled with peanuts is fixed to a tree, and it seems like a peaceful little snack station for squirrels. But hidden in plain sight is the twist: there's actually a real squirrel sitting among the peanuts, almost invisible to the untrained eye.

The challenge? Spot the squirrel without any hints. Many people have spent several minutes staring at the image, convinced there's no animal there a...