This is the Coffer Illusion and comes to us via the wonderful Juanita Broaddrick and X.
Coffer refers to the 20 squares most initially see that resemble coffers or recessed ceiling panels.
The illusion takes effect when the 20 squares become 16 circles.
This was a finalist 2006 Best Illusion of the Year Contest and submitted by Anthony Norcia, a psychology professor at Stanford University.
