Hermann grid illusion
The Hermann grid optical illusion was discovered by Ludimar Hermann in late 19th century. When focus on this image see grey squares/elements in the white intersections but when trying to focus on the dots they quickly disappear again.
Lingelbach scintillating grid illusion
The Hermann grid illusion is often mixed up with the scintillating grid illusion that was created first in 1994 by E. Lingelbach. The Lingelbach scintillating grid illusion is based on the same grid pattern as the Hermann grid illusion but contains white circles at the intersections of the lighter white lines. The white circles in contrast to the black elements make dart dots appear on random white discs not in focus.