The image below has 12 dots overlayed on a grid of intersecting grey lines. But, because of how your retinas are wired up inside of your eyes, you can likely only see a couple at one time, and when you try to look at the others, the dots appear to start moving. It’s unsettling.
“Ninio’s extinction illusion” is currently blowing minds across the internet, with some users reporting to see all 12, but most, reporting that they are moving everywhere within the pattern. Either way, take a few moments and have your eyes play tricks on you.