The illusion in view by staring at the small black dot for a half minute or so, then switching to the white dot. The black squares appear stationary when staring at the white dot, but a fainter grid of moving squares also appears to be present.
Hermann-Hering Illusion
See also
Hering Illusion, Hermann Grid Illusion, Scintillating Grid IllusionExplore with Wolfram|Alpha
References
Hering, E. Grundzüge der Lehre vom Lichtsinn. Berlin, Springer-Verlag, 1920.Referenced on Wolfram|Alpha
Hermann-Hering IllusionCite this as:
Weisstein, Eric W. "Hermann-Hering Illusion." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Hermann-HeringIllusion.html