SAMUEL M. ALLEN is Professor of Physical Metallurgy in the Department of Materials Science and Engineering at M.I.T. He earned a Bachelor of Engineering degree from Stevens Institute of Technology and an S.M. and a Ph.D. from M.I.T. His research interests include phase transformations, solid/solid interfaces, structure/property relations in high-temperature alloys, three-dimensional printing of metal tools for plastic injection molding, and alloys for high-strain actuators. He is also co-authoring a graduate textbook, "Kinetic Processes in Materials," with Robert W. Balluffi and W. Craig Carter. EDWIN L. THOMAS is the Morris Cohen Professor of Materials Science and Engineering at M.I.T. He received a B.S. in Mechanical Engineering from the University of Massachusetts and a Ph.D. in Materials Science from Cornell University. His research interests include processing, microstructure and mechanical property relations of polymers, and optical properties of liquid crystals and polymeric-based photonic band gap materials. Professor Thomas' honors and awards include the High Polymer Physics Prize of the American Physical Society and the American Chemical Society Creative Polymer Chemist Award.