See how about three or four dots appear to move? Pretty trippy, right?
As explained in a report by Sploid, the bizarre image is called Ninio's Extinction Illusion, which is basically a variation of the equally maddening Hermann Grid Illusion. The illusion actually includes 12 dots that are placed at the intersections of vertical, horizontal, and diagonal gray lines. But thanks to the way the light receptors in your eyes work, there's a good chance you can only see three or four of the dots at the same time. A recent video from DNews offers a detailed breakdown on how optical illusions like this work.
Here's how Ninio describes how the illusion manages to fool your eyes and brain, per the abstract from a scientific paper published back in October of 2000:
"When the white disks in a scintillating grid are reduced in size, and outlined in black, they tend to disappear. One sees only a few of them at a time, in clusters which move erratically on the page. Where they are not seen, the grey alleys seem to be continuous, generating grey crossings that are not actually present. Some black sparkling can be seen at those crossings where no disk is seen. The illusion also works in reverse contrast."
The illusion soared in popularity on Reddit on Monday after it was shared by game developer Will Kerslake via Twitter on Sunday night and Japanese psychology professor Akiyoshi Kitaoka via Facebook on Sunday morning, according to a report by BBC.