What are atoms? We can't even see them, so how do we know they are real? This book introduces readers to the concept that atoms are everywhere and that everything is made up of them. Readers will learn the history of atomic theory, from early Greek philosophers through John Dalton and Niels Bohr and on to current researchers in the field. Students will encounter high-tech tools such as the atomic force microscope and discover how scientists and engineers solve atomic problems. Colorful photographs and diagrams help make complex scientific concepts more accessible to elementary readers.