Many professors and students at MIT and Stanford University have helped refine the technical ideas underlying this book. Thanks also go to technical audiences at laboratories in the United States, Japan, and Switzerland for their critiques of these concepts.

A number of friends read early drafts and made suggestions for improving the accessibility of the book: James C. Bennett, Linda Boyd, Stewart Brand, Heidi Christensen, Allan Drexler, Helene Brun, Roger Duncan, Stan and Kiyomi Hutchings, Peggy Jackson, Jackie Kubal, Ralph Merkle, Russ Mills, Janice Morningstar, Ed Niehaus, Harold and Joy Pergamit, Amy Peterson, Gordon Peterson, Norma Peterson, Dave Ross, Heidi Wheelock Ross, Tracy Schmidt, Sue Schumaker, Carol Shaw, Leif Smith, and Marc Stiegler. To Barry Silverstein go special thanks for support during the writing of this book.

Thanks also to our transcriptionist Cheri Fjermedal, artist Pauline Phung, agent John Brockman, and editor Doug Stumpf.