Marc De Graef is a Professor in the Department of Materials Science and Engineering at Carnegie Mellon University in Pittsburgh, USA, where he is also Co-director of the J. Earle and Mary Roberts Materials Characterization Laboratory. He received his Ph.D. in Physics in 1989 from the Catholic University of Leuven. An accomplished writer in the field, he is on the Board of Directors for the Minerals, Metals and Materials Society (TMS). Michael E. McHenry is Professor of Materials Science and Engineering, with an appointment in Physics, at Carnegie Mellon University in Pittsburgh, USA. He received his Ph.D. in Materials Science and Engineering in 1988 from the Massachusetts Institute of Technology, before which he spent three years working in industry as a process engineer. Also an accomplished writer, he is Publication Chair for the Magnetism and Magnetic Materials (MMM) Conference.