Macbeth extolled “sleep that knits up the ravell’d sleave of care,” in Shakespeare’s great tragic play of the same name. Soothing rest is not all that shut-eye provides, however. As sleep and cognition researchers Robert Stickgold and Jeffrey M. Ellenbogen explain in their feature article in this issue, the brain is very busy during a night’s slumber. It is processing and sorting all the things we learned during the day, making valuable memories more resilient and tossing away irrelevant details. It finds hidden relations among our recollections and works to solve problems that arose during our waking hours. Turn to page 22 for our cover story, “Quiet! Sleeping Brain at Work.”

There is nothing like a good yarn to pluck our emotional strings, as Jeremy Hsu writes in “The Secrets of Storytelling,” beginning on page 46. Stories are one of humanity’s universals—they appear in all cultures—and certain themes arise repeatedly in tales around the world. Why do these narratives have such power over our feelings? The study of stories reveals clues about our evolutionary history and the roots of emotion and empathy. Indeed, as you will learn from Hsu’s article, the stories we tell explain much about ourselves.