This isn't your run-of-the-mill brainteaser, though - this one requires some effort.
Dr. Michelle Dickinson, a nanotech engineer (and kite-surfer) posted the illusion on Twitter, telling her followers "I'm serious" about shaking their heads.
Can you see the illusion?
Spoiler alert, it's a cat.
If you're trying to avoid a headache, or shaking your head in the office to the confusion of your co-workers, there are a few other ways to try and see the cat.
First, instead of shaking your head, you can try moving the picture back and forth on your screen. This simulates the movement without giving yourself a pounding headache.
If that doesn't work, try looking at the photo from different angles (though, that might still earn you some stares).
If all else fails: zoom out on the photo. If you look at a very small version, the cat should become clear.
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