Scintillating grid illusion. This illusion, based on the Hermann grid, was created in 1994. When the grid is observed, the white dots at the intersection of the grey lines appear to scintillate - flickering between black and white. If a single white dot is stared at for a while the effect disappears. It is thought to be caused by the processing that takes place in the eye and the brain to produce the final image that we perceive.