The carbon cycle is followed through all its stages. The idea of the book is to present an elementary idea of the atom and the choice of this substance makes the book an excellent re-enforcement to the simplest approaches to biology and chemistry concepts as well. The text is very clear and moves from introductory point to logical conclusion with the case for which Mrs. Selsam is noted. It is in the illustrations and diagrams that you perceive the complexities which cannot be simplified past a given point. They are labeled, they are large, but they are the same structural drawings and molecular mock-ups to be encountered in highschool texts. This is basic material and required for today's accelerated science programs. For a good reader, well taught at the third grade level, the book will be just what the teacher ordered.