STEPHEN ALVAREZ, who has captured some of the most rarely seen objects on earth, is a photojournalist who produces global stories about exploration, culture, religion, and the aftermath of conflict. He has been a National Geographic photographer since 1995. His pictures have won awards from Pictures of the Year International and Communication Arts and have been exhibited at Visa Pour l'Image International Photojournalism Festival in Perpignan, France. SUSAN TYLER HITCHCOCK is a senior editor in the Books Division of the National Geographic Society, where she is responsible for science, health, and nature titles. She has written 16 books, from literary history to personal memoir. This is the third National Geographic photography collection to which she has contributed. She lives in Covesville, Virginia.