Troxler's fading

Imagine you're looking at a picture of a cute puppy that's painted on a wall. At first, you can see all the colors and details of the picture - the puppy's fur, eyes, nose, and everything else. But, as you keep looking at the picture for a few minutes, some parts of it will start to disappear or fade away, especially the ones that aren't moving or changing.

Troxler's fading is a fancy name for this phenomenon, which happens because of how our eyes and brain work together. When we stare at something for a long time, the cells in our eyes that detect colors and shapes get tired and stop sending as much information to our brain. That makes our brain think that those parts of the picture aren't important, so it ignores them and focuses on other things.

This is why some parts of the picture seem to fade or disappear, even though they're still there. It's not because the picture is changing or moving, but because our eyes and brain are filtering out some of the details that they don't think are important anymore.

Troxler's fading can happen with other things too, like words on a page, a spot on a wall, or even a sound that you've been hearing for a while. But don't worry, it's perfectly normal and nothing to be scared of. Just take a break and look away for a few seconds to let your eyes and brain rest, and everything will be back to normal again!