Your eyes get heavy and gradually close… But wait! It’s only lunch time and you still have so much to do. Would taking a nap help? Or would it derail your day? Well, that depends on a few things— especially what stages of sleep the nap includes. Sara C. Mednick details the cognitive benefits of napping, and explores the optimal length and time of day for a quick snooze. Lesson by Sara C. Mednick, directed by Qian Shi.