This is the first unit of a 15-unit School Mathematics Study Group (SMSG) mathematics text for high school students. Topics presented in the first chapter (Structuring Space) include: lines and points; planes; intersections; intersections of lines and planes; betweenness and segments; separation; angles; locating positions and points; coordinates; coordinates in the plane; and graphs in the plane. Topics presented in the second chapter (Functions) include car travel; falling objects; examples of functions; ways of representing functions; discovering the usefulness of graphs; the identify functions; and new kinds of functions. (JN)