Bengt Sjölén and Adam Somlai Fischer, along with artist-cum-researcher Usman Haque, have developed the Wifi Camera to explore this invisible realm and how we move about it. By pointing a series of Wi-Fi antennas at a given space, the "camera" records the signal strengths of wireless transmitters and visually maps their expanse and movement. Waves at the Wi-Fi wavelength act similarly to visible light, bouncing off of solid objects and passing through transparent ones. And since Wi-Fi operates on radio waves, radiation from microwaves and cell phones (which rely on radio, too) appear in the picture, as well. Check out a demonstration of one Wi-Fi Camera rig below. The team says on their site that they are working toward video capability; that would be fascinating indeed, since they are currently able to "see" people amidst the radiation, but only statically.