One of my favorite interactive art installations, this is Daniel Rozin's "Wooden Mirror." Its function is exactly like a real mirror, but it creates the shape and value of your likeness with 830 tiny panels of wood instead of glass. The way it works is there is a camera fitted to the wooden frame of the mirror that captures the visual data and sends that information to a computer. The computer then interprets the visual feed and rotates the wooden panels, each with its own motor, to best represent what the camera is seeing. Rozin made it in 1999 and it's been around a few places on display. I've never seen it in person myself, but I've been dying to go.