You've probably heard of lucid dreaming. In a nutshell, dreaming lucidly means being aware that one is dreaming, and nonetheless keeping on with the dream—instead of waking up saddened to realize that you're not really riding that hippo.

The mechanism was explored in Christopher Nolan's 2010 film Inception, which ultimately resulted in gigas of internet discussions on the concepts of dreams and reality (was that spinning top twirling or not?). At some point in the movie, a character starts doubting whether she's awake or still inside a lucid dream—eventually getting badly hurt. While that scenario would be a stretch, lucid dreaming experts agree that the experience can be extremely realistic: In fact, they think that lucid dreaming is one of the best life simulators available.