Do you see what I see?
First notice that the two desert scenes have exactly the same colour composition. The skies are both blue-ish and the deserts are both yellow-ish.
Stare at the dot between the red and green squares for 60 seconds, and then look back at the dot between the two desert scenes.
The more focused you are in staring at the dot between the green and red squares the better the subsequent illusion will be.
The illusion was created by neuroscientist Beau Lotto (website here, with more illusions).
(Are you colour blind? Do you see any effect from this illusion?)
I have a feeling that this effect could be used in some sort of cool Instructable, but I have no idea what...