All artwork by Christina Balit unless otherwise noted below.
Cover (LO), Nata-Lia/Shutterstock; 1.1 (LE), Carmen Martinez Banus/Getty Images; 4.1 (RT), Duby Tal/Albatross/Alamy; 6.1 (RT), The Image Bank/Getty Images; 8.1 (RT), Mary Evans Picture Library/Alamy; 9.1 (LE), Andreykuzmin/Dreamstime; 11.1 (LE), Ivy Close Images/Alamy; 14.1 (LE), Getty Images; 15.1 (LE), Dimitri Vervitsiotis/Getty Images; 17.1 (LE), Abam Jiwa AL-Hadi/Getty Images; 18.1 (LE), Granger, NYC—All rights reserved; 21.1 (RT), Stock4B-RF/Getty Images; 22.1 (CTR RT), Said Khatib/AFP/Getty Images; 22.2 (CTR LE), ephotocorp/Alamy; 24.1 (RT), Moment RM/Getty Images; 25.1 (LE), Matyas Rehak/Shutterstock; 27.1 (LE), Rhapsode/Getty Images; 29.1 (RT), AFP/Getty Images; 31.1 (RT), Jose B. Ruiz/NPL/Minden Pictures; 32.1 (LE), Gallo Images/Getty Images; 34.1 (RT), Waterframe/Getty Images; 35.1 (RT), Oleg Zaslavsky/Shutterstock; 36.1 (LE), Natig Aghayev/Shutterstock; 37.1 (LE), Jodi Cobb/National Geographic Creative; 38.1 (RT), Vetta/Getty Images; 38.2 (RT), Science Source/Getty Images; 39.1 (LE), Robert Harding World Imagery/Getty Images; 43.1 (LE), Vetta/Getty Images; 45.1 (LE), Granger, NYC; 48.1 (LE), Alex Treadway/NG Creative