The first edition of this popular book on particle physics received universal acclaim for its clear and readable style. In this second edition the authors have brought the subject right up to date, including the recent discovery of the 'top quark' and the search for the Higgs boson. The book is the result of a collaboration between a world-famous elementary particle physicist and a physicist specializing in popular science writing. Together they have produced a fascinating account of the search for the fundamental building blocks of matter. Beginning with the experiments of Thomson and Rutherford at the turn of the century, the book chronicles how physicists revealed layer upon layer of structure within the atom, and culminates in a completely up-to-date description of current theories, which form the 'Standard Model' of particle physics. All that is required of the reader is a basic knowledge of a few key concepts, such as energy, mass and electric charge. The principles and concepts of the two great physics theories of the twentieth century - special relativity and quantum mechanics - are lucidly described, as are the basic concepts of atomic and subatomic physics. The book is written from the perspective of a physicist who played an active role in the development of the subject, and is spiced with interesting and first-hand stories and anecdotes relating to some of the leading figures in the field.