JULIE BEER is a long-standing contributor to National Geographic Kids. Her works include Penguins vs. Puffins, Piglets vs. Pugs, multiple books in the hit Weird But True! and 5,000 Awesome Facts series, This or That? 4, Get Outside Guide, and Ultimate Explorer Field Guide: Birds, among others. She currently lives in northern California with her two daughters, a dog, a cat, and a guinea pig.