A primer on the evolution of particle physics and the search for the fundamental building blocks of matter. The book presents the full current body of understanding of particle physics in way accessible to a reader with some basic principles of physics (energy, momentum, electrical charge). This concise book tells the fascinating story of how 20th century physicists revealed layer upon layer of structure within the atom to reach the basic particles of matter, and then culminates in descriptions of current theories which form the Standard Model and the discovery of the top quark. Includes chapters on cosmology. Book includes many illustrations and photographs, and integrates the stories of the individual scientists throughout. Includes 4 color photographs, and the famous "Particle Chart". The book is a collaboration among eminent physicists (including J.D. Jackson and G. Goldhaber) at LBL, CERN and high school teachers in the Contemporary Physics Education Project to develop a novel book to teach particle physics to students.Book can thus be used as a supplement for courses in advanced high school and physics courses.