2014's Nobel Prize for Physiology or Medicine has been awarded to John O'Keefe, May-Britt Moser, and Edvard Moser for their discovery of the brain's 'inner GPS' system. The prize revolves around their discovery of place cells and grid cells in the brain that appear to create a cognitive map of every room or space that you've ever explored. As you move around a room or space, a very specific place cell fires -- and when you visit the same place again in the future, the same place cell fires every time.