So, Yea. 

In this image, there are twelve black dots where the gray lines meet, but people are having quite a bit of trouble seeing all 12 dots simultaneously. They appear to be blinking in and out of existence.

Japanese psychology professor Akiyoshi Kitaoka first posted the optical illusion in early 2023 on Facebook, but the origin of this bit of visual trickery is a scientific paper published in the journal Perception in 2000.

To be clear, there really are 12 black dots in the image, but the black dots around it seem to appear and disappear. That's because humans have pretty bad peripheral vision. 

According to the scientific paper, "It's sort of an existential crisis."

 That means that when you're staring at that black dot in the center of your field of view, your visual system is filling in what's going on around it. And with this regular pattern of gray lines on a white background, the brain guesses that there'll just be more of the same, missing the intermittent black dots. Those dots disappear and reappear as your eye jitters around like an unstable camera.

The study also points out another thing that could be going on. If you look at the grid pattern closely, you might be able to see faint white squares where the gray lines meet. That's similar to the dark patches you can see at the intersection of white lines in the Hermann grid illusion. This happens because retinal ganglion cells in the sheet of tissue called the retina at the back of the eye detect contrasts.

The study adds that we still need to learn a lot more about the mental computations that give rise to visual perception. But the great thing about optical illusions is they're a peculiarly fun tool for figuring it out.