There are 16 circles in this picture. Can you find them?

Everyone loves a good optical illusion and this is one of the best that we've seen.

A tweet from Dr Gavin Buckingham has gone viral in the past few days and its got people scratching their heads.

Within the illusion, which on the surface looks like a series of black and grey rectangles surrounded by lines, are 16 circles.

It might not be apparent at first but we assure you that they are there.

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Go on, give it a try.

Having trouble? Just relax your eyes and try to look at every area of the image from whatever angle you may choose.

Even if it takes you hours, you'll get there eventually.

Optical illusions are created by a combination of colour, light and patterns which are designed to confuse the brain so it cannot comprehend what the eyes are seeing.

This particular illusion is known as the Coffer Illusion, and plays with the fact that the mind is geared towards identifying shapes that are grouped to form edges and contours.

For most people the collection of rectangles will be the most apparent as it is a shape that we are more familiar with; think doors, phones, computers etc.

After a while you should be able to see the circles, and once you can it'll be hard to not see them.

How long did it take you to see the circles? Let us know in the comments below.

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