Virtual-reality headsets, like the Oculus Rift, create escapes. Put one on, and you’re suddenly swimming with dolphins or fighting in the Battle of Waterloo. Microsoft’s HoloLens, by contrast, augments reality — overlaying holograms and data onto existing surroundings, so you’re not «confined to the virtual world,» as designer Alex Kipman puts it. Imagine gamers defending their homes from robot invaders, engineers manipulating 3-D models or surgeons following directions «on» the human body. Early tests indicate all are possible. Already the HoloLens is being used by NASA to mimic Mars’ terrain in labs and by medical students to dissect virtual bodies.