Illusory Blue Dots by Akiyoshi Kitaoka
In this variant of the Hermann grid illusion created by Professor Akiyoshi Kitaoka, illusory blue dots can be seen in the white circles where the squares intersect. This phenomenon was first reported in 1870 by Germany physiologist Ludimar Hermann. The blue dots cannot be seen if you look directly at one of the white circles. Instead, you will only see the blue dots in the circles that you are not focusing directly on. While I would not recommend it, you could move your eyes around the grid “chasing” the illusory blue dots forever.
(via Akiyoshi Kitaoka)