There is no glue, no cutting—only precision, patience, and a deep understanding of form.

Ah, optical illusions. It seems the internet's appetite for having its collective mind boggled by all manner of brain-twisters will never abate – but it isn't every day that we see illusions as ...

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.