While new optical illusions go viral all the time, here are some of the most famous illusions that have kept us scratching our heads for years.

Optical illusions occur naturally in different habitats and conditions across the world. Cloud formations can sometimes make it seem like there's an ocean or a UFO in the sky. Whether it is salt flats ...

Sometimes things are not what they seem. They become poetic thanks to optical illusions. Have a look at this collection of ...

Optical illusions are great fun, and they fool virtually everyone. But have you ever wondered if you could train yourself to unsee these illusions? Our latest research suggests that you can. Optical ...

The famous Ebbinghaus illusion, named for its discoverer, the German psychologist Hermann Ebbinghaus (1850–1909). Despite appearances, the two orange circles are the same size. Have you ever looked at ...

Allen Institute researcher Jerome Lecoq points to one of the diagrams that was used in a study focusing on how the brain interprets optical illusions. (Allen Institute Photo / Erik Dinnel) Our brains ...

Everyone loves an optical illusion — even if they leave us completely stumped — and they're all around us in the natural world. From an underwater waterfall in the Indian Ocean to a surrealist scene ...