The illusion consists of a patterned set of blue and red circles, set out like a target against a black background. It's meant to appear in 3D (when of course it is completely flat). It's a version of an illusion I've seen before that's very similar but completely plain - and that one always causes division too. Some people blame astigmatism for their failure to see the illusion's effect while others have no explanation.
Optical illusions come in many different forms, from the perplexing to the mind-melting, but op art doesn't always have to be headache-inducing. Representing the serene side of op art, Larry June's Life is Beautiful LP is a mesmerising visual treat with a delightfully smooth soundtrack to match. From the cognitive to the physiological, optical illusions are typically caused by our brain misinterpreting information, leading to visual displays that amaze and confuse.