Below, the two pictures it is made from: a blurred Marilyn Monroe, and only the fine lines of Albert Einstein.
Two pictures in one
Hybrid image
Whose face is this?
Up close, Albert Einstein. Step back across the room, or squint: it becomes Marilyn Monroe.
Why? The picture mixes the fine details of one face with the blurry outline of another. Up close you see the details; from far away only the blurry shapes reach you.
Picture: Wikimedia Commons, Public domain · Wikipedia(opens in a new tab)