> Movement
> Anatomic phenomena
> Shapes
> Contrasts
> Colours

Shapes

The café wall effect
This phenomenon was first noted on the wall of a café - hence the name. What is happening? > more
The Hermann grid
A grid with black, flickering spots which suddenly disappear. There is a reason for everything. > more
Fraser's spiral
The spiral shown really only consists of segments of a circle. How is the false impression given? > more
Escher's stairs
Why do the stairs go continuously up or down? A unique optical illusion. > more
Necker cube
The cube has been drawn so that the viewer has two perception "options". > more