There are 30 pages in this book. This is a reference book. This book was published 2008 by HarperCollins Publishers Inc .

Franklyn M. Branley was the originator of the Let's-Read-and-Find-Out Science series and the author of close to 150 popular books about scientific topics for young readers of all ages. He was Astronomer Emeritus and former Chairman of the American Museum of Natural History-Hayden Planetarium. Michael Rex learned to draw in Chatham, New Jersey, and studied at the School of Visual Arts in New York City. Who Digs? and Who Builds? are his first two books with HarperCollins. Mr. Rex lives in Brooklyn, New York.