Afterimage

Afterimage is something that happens when you look at something bright for a while, then look away and can still see a faint version of the thing. It's like a ghost image of the thing you just looked at. It happens because when your eyes look at something bright, it causes the cells in your eyes to get excited and turn on. After you look away, those same cells stay excited for a while and still make an image, even though the thing you were looking at isn't there anymore.