This supplement to the Macmillan Encyclopedia of Physics presents the most recent data on particle physics, a field that has seen many important breakthroughs since the publication of the parent set in 1996. The work reviews all observed and theoretical particles known to date, retracing the history of each particle's discovery and function, and covers current research; practical applications both hypothetical and actual; and provides biographical entries on scientists who made significant contributions to the field. Case studies and experiments round out the broad range of topics covered.