A coloured picture of a group of teenagers has gone viral – and the reason why is quite baffling.
At first glance, the snap shows the pals posing together as one of them is holding a tortoise.
But what you don’t realise is that the image is actually an optical illusion which means it’s technically in black and white.
Digital artist Stuart Humphryes shared it on Twitter explaining how it demonstrates the “colour assimilation grid illusion”.
The London-based content creator simply added a grid featuring colourful lines over the black and white image.
He explained how our brains “fill the gap” of colour perception and apply the grid colour to the rest of the picture.
In the shot, the teenagers T-shirts look green, blue, yellow or red, and the tree behind is green.
But on closer inspection, you can see the snap is actually greyscale without any colours on their clothes or surrounding nature.
Since Stuart shared this information to his 158,700 followers on Twitter, it racked up over 15,800 likes and 4,700 retweets.
And it’s safe to say that many people were left mind-blown at the revelation.
He said: “This is fascinating and shows how weak colour information can be for the brain to fill in the gaps and ‘colourise’ it for you.
“It’s a black and white photo, but overlaid with a thin grid of coloured lines.
“They’re enough to trick your mind into seeing a full colour image.”
One said: “That’s extraordinary,” while another added: “Needn’t have bothered buying a colour TV.”
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The user continued: “Could have just drawn some red lines on the black and white one.”
A third amazed fan wrote: “That’s quite unsettling but amazing.”
In another optical illusion, a TikTok user explained the myth behind an “impossibly steep” bridge.
Meanwhile one image shows coloured spots moving – but not everyone sees them.