The concept of virtual or simulated reality has a rich history. In fact, depending on how you define your terms, the idea of reality as being essentially unreal goes back pretty far -- all the world's a stage, and so forth. Technology-driven virtual realities have become of fixture of many science-fiction movies, where the visual nature of the medium is ideal for suggesting the immersive world of VR.
Virtual realities need not be strictly computer simulations -- phantom digital worlds existing only in cyberspace. Simulated realities could employ science from a dozen different disciplines -- neurology, optics, nanotechnology, material sciences. We look at some of the weirdest VR worlds in science-fiction films and the real-world technology currently under development that is moving us toward them.