Smartphone apps including Calm and Headspace offer “sleep stories,” or audio tales that are designed to put the listener to sleep.

“There aren’t high stakes, there aren’t big revelations … they’re very gentle stories, and they just gradually wind down and guide the listener off to sleep,” says Calm’s Advansun.”I think what a sleep story is doing on a very subconscious level is … replicating that experience that many of us had of being a kid and having a loved one, who we trust so much, tuck us in at night, and read a story. And we’re drifting off to that comforting voice.”