Nine years has passed since the 1992 second edition of the encyclopedia was published. This completely revised third edition, which is a university and professional level compendium of chemistry, molecular biology, mathematics, and engineering, is refreshed with numerous articles about current research in these fields. For example, the new edition has an increased emphasis on information processing and biotechnology, reflecting the rapid growth of these areas. The continuing Editor-in-Chief, Robert Meyers, and the Board prepared a new topical outline of physical science and technology to define complete coverage. Section editors are either Nobel Laureates or editors of key journals in their fields. Additional Board members representing the global scientific community were also recruited.