Sharon Katz Cooper is a science educator and freelance writer who specializes in science and social studies topics. She has written more than 25 books for children, including a series called Horrible Habitats, which was recommended by the National Science Teachers Association (NSTA). She is based in Pittsburgh, Penn., where she lives with her husband and three boys, Reuven, Judah, and Yaron. Christina Wald has done illustration for a wide variety of toys, games, books, and magazines-everything from board books and pop-up books to Star Wars role-playing games and G.I. Joe package art. She studied Industrial Design at the University of Cincinnati. When she is not in the studio, Christina is out urban sketching, biking, and/or traveling. She lives in Cincinnati with her toy engineer husband, Troy, and two cats.