Credits

ROYAL REST Princess Diana nodded off at an exhibition gala at the Victoria and Albert Museum in 1981.

Cover

Ljupco/iStockphoto/Getty Images

Back Cover

(from top) feelartfeelant/Shutterstock; Kateryna Kon/Science Source; Neustockimages/E+/Getty Images

Title Page

Juliana Sohn

Contents

Ted Spagna/Science Source/Getty Images

Introduction

4 RubberBall Productions/Brand X Pictures/Getty Images

What Sleep Is For

7 Illustration by Timothy Goodman 10 Courtesy University of Rochester Medical Center 13 (from left) Oliver Rossi/The Image Bank/Getty Images; Steve Cole/Vetta/Getty Images; Mike Powell/Stone/Getty Images

Doctor’s Orders

15 Kathy Quirk-Syvertsen/Photographer’s Choice RF/Getty Images 17 Seth Joel/Science Source 18–19 Tom Penpark/DigitalVision/Getty Images

Getting to Bedtime

21 Lorado/E+/Getty Images 22–23 Juliana Sohn 25 JGI/Tetra images RF/Getty Images

The Teenage Brain

27 Image Source/Alamy 28–29 Timothy Devine 31 Hero Images/Getty Images

Bad Dreams

33 Lincoln Agnew/www.marlenaagency.com 35 PeopleImages/E+/Getty Images 36 Louis Psihoyos/www.psihoyos.com 39 Fine Art Images/Heritage Images/Getty Images

Sleep Like a Pro

41 g-stockstudio/iStockphoto/Getty Images 43 Rob Carr/Getty Images 44 The Image Bank/Getty Images

Animal Slumbers

47 FLPA/Kevin Elsby/Shutterstock 48–49 (clockwise from top) Devilkae/iStockphoto/Getty Images; Natalia Pryanishnikova/Alamy; Design Pics Inc./Alamy 50–51 (clockwise from top) Frans Lanting/Mint Images/Science Source; Norbert Wu/Minden Pictures; Tui De Roy/Minden Pictures 52–53 (clockwise from top) Peter Kelly/EyeEm/Getty Images; Remus86/iStockphoto/Getty Images; Brian Gordon Green/National Geographic Image Collection

Sleeping Pills

55 Jacques LOIC/Photononstop/Getty Images 56–57 Jekaterina Nikitina/DigitalVision/Getty Images 60–61 Dieter Spannknebel/Stockbyte/Getty Images 62 Kate Holt/eyevine/Redux 63 Zackary Canepari/VII/Redux

Goodnight Gadgets

65 Nanit 66 (from left) Courtesy Philips; Andrew Meyers for TIME 67 (from left) Courtesy Soraa; Patrick T. Fallon/Bloomberg via Getty Images 69 Dave Kotinsky/Getty Images for Fitbit

Creativity

71 Phillip Toledano 72 Pete Turner/Hulton/Getty Images 73 Fritz Henle/Science Source 74 MGM/Kobal/Shutterstock 75 Jannis Werner/Alamy 76 Image Source Plus/Alamy 77 Seth Joel/The Image Bank/Getty Images

Sleep Studies

78 Vincent Besnault/Photographer’s Choice/Getty Images 79 AnastasiaNurullina/iStockphoto/Getty Images 80 Patrik Giardino/Corbis/Getty Images 81 (from top) KTSDESIGN/Science Photo Library/Getty Images; Iryna Imago/iStockphoto/Getty Images 82 (from top) Shannon Fagan/The Image Bank/Getty Images; Basak Gurbuz Derman/Moment RF/Getty Images 83 Phanie/Alamy 84 Jose Luis Pelaez Inc/DigitalVision/Getty Images 85 Tpopova/iStockphoto/Getty Images Plus

A World of Slumber

86–87 Jon Woo/Reuters 88 Emin Ozmen/Magnum Photos 89 Maggie Steber/National Geographic Image Collection 90–91 Damir Sagolj/Reuters 92 Corey Rich/Cavan Images 93 Munir Uz Zaman/AFP/Getty Images 94 (from top) STR/AFP/Getty Images; Marco Del Grande/Fairfax Media via Getty Images 95 Tim Graham/Tim Graham Photo Library/Getty Images 96–97 Bridgeman Images