Oh look. It's a bunch of squares. Wait a minute. In a mirror, they look like a bunch of cylinders. Has the world gone mad? Don't worry. You haven't fallen down the rabbit hole. It's just a very clever optical illusion called "Ambiguous Cylinder." It's also a well-deserved finalist for the Best Illusion of the Year Contest, an event run by the Neural Correlate Society, an "organization that promotes scientific research into the neural correlates of perception and cognition."
The cylinder/square trick comes from Kokichi Sugihara, an engineering professor at Meiji University in Japan. "The direct views of the objects and their mirror images generate quite different interpretations of the 3D shapes," reads the illusion's description. It's a playful way of messing with human perception and viewing angles.
We all know the internet loves a good illusion, as proven by a recent freak-out over a photo of a brick wall and Twitter's fascination with a cat strolling through a desert. For more optical-illusion fun, check out the contest's first-place winner, "Motion Integration Unleashed: New Tricks for an Old Dog."