Eye-to-Eye
Photographs (clockwise from upper left) David/Haring/Duke University Primate Center; Stephen Frink/Corbis; Renee Lynn/Getty Images; Desmond Burdon/Getty Images

Going Green
Photographs (clockwise from upper left) by: Hoa Qui/Index Stock Imagery; Gerry Ellis/Digital Vision/Getty Images; Digital Vision/Getty Images; Hal Beral/Corbis

Stackables
Game by Oddtoe, Illustration (Chihuahua) by Nathan Jurevicius