In a dark room, in the middle of the night, a woman lies dreaming. Suddenly, her eyes beneath their lids dart crisply left-right, left-right. The eye signal means she knows she’s dreaming. Lucid ...

The busy box that is your brain is hard at work all day long—and it doesn’t quit when you’re asleep. Not only does your brain fill your slumber with dreams, it also goes right on solving the problems ...