Backstage at this illusion, in a video, Penn admits that medical science isn't keeping Teller's head alive. Optics, the science of mirrors, drives this illusion.

A large mirror propped in front of Teller's body leaves his head visible. The predictable properties of mirrors—light bounces off it at the same angle it arrives, and a mirror image appears as far behind the mirror as the real thing is in front—let us set up the mirror to control what you see.

The mirror is exactly between the front and the back walls, which are painted the same. So while you think you're looking under Teller's head to the back wall, you're really seeing a reflection of the front wall. And the checkered floor helps the illusion too, with the lines coming closer together in the "distance" just as you'd expect. The story of Teller's accident and the art of Penn & Teller's performance make the illusion complete.

So now you know what creates this illusion: plain old mirrors—right? Well, Penn then introduces some other astonishing illusions with heads that won't stay attached to a body, all with no mirrors involved.

You can also use mirrors backstage to create a fantasy creature, and experiment with mirrors to explore the angles of reflection. Also, you can go into the same illusion set used by Penn & Teller and be the Living Head—make sure your family takes a picture!