In this demonstration of the touchable hologram, ultrasound is radiated from above and the user feels as if a rain drop hits his palm.Researchers from the University of Tokyo have developed 3D holograms that can be touched with bare hands. Generally, holograms can't be felt because they're made only of light. But the new technology adds tactile feedback to holograms hovering in 3D space. http://www.youtube.com/watch?v=Y-P1zZAcPuw