Researchers have figured out how to make people aware of themselves during a dream: by zapping their sleeping brains with a weak electric current.

The sensation of "Hey, this is a dream!" is known as lucid dreaming. Those who naturally become lucid while dreaming, probably a small segment of the population, also report adventures that are impossible in the real world, such as flying, that feel completely real. Some can even change a dream's narrative twists and turns to make it less scary—or even more exhilarating. (Related: "Why Do We Dream? To Ease Painful Memories, Study Hints.")

Lucid dreaming is exciting not only for dreamers but also for neuroscientists, who consider it a window into the study of consciousness. But until