They are the world's fastest land animal and one of its most arresting—"the supermodels of the cat world," photographer Mark Segal says—but cheetahs are also in critical danger. Thanks to trophy hunting and habitat loss, their population has plummeted from 100,000 in 1900 to only about 7,000 today. Spurred to action, Segal—a lifelong wild cat aficionado—went on a five-year journey photographing these big cats in the wild and in captivities across Africa, Europe, and North America. The result is a new book, Cheetah (Damiani), a gorgeous, surprisingly intimate look at this mysterious and playful feline. "I approached photographing the cheetahs as I would a person—as a self-aware, emotional individual," Segal explains. "I want people to see their individual beauty, their strength, and their vulnerability." All of the book's proceeds go to conservation programs, such as the Cheetah Conservation Fund in Namibia, which, in rebuilding habitats and educating local communities, not only saves cheetah lives, but improves human ones as well.