Every living thing on the planet is comprised of cells. Even the smallest bacterium or virus is made up of one cell. By studying the cells of various living things, scientists can learn how to keep people healthy, how to treat disease, and even how to enhance crop growth and nutrition. This volume takes an in-depth look at the ways cells differ among various organisms and how they function. Eye-catching graphic organizers and informative fact boxes give young readers information that is crucial to understanding how the environment affects their body and provides an early foundation for future careers.