Afterimages occur when the photoreceptors in our retina are stimulated by light. They translate this stimulus into electrical impulses through a chemical reaction. These phantom images are still felt even when the original stimulus has faded away. They are usually perceived as bright spots after looking at the sun or another light source.
For that fun project I experimented with positive afterimages, documenting the colors and shapes I saw in my mind’s eye after looking into different light sources.