Herman P. van Leeuwen is an electrochemist who obtained his degree in chemistry at the State University of Utrecht, The Netherlands, in 1969. His thesis was in the field of pulse methods in electrode kinetics, and his Ph.D. degree was awarded cum laude (best 5% in The Netherlands) in 1972. He then joined the Colloid Chemistry and Electrochemistry group of Professor J. Lyklema at Wageningen University, where he became a senior lecturer in 1986. His teaching includes analytical/ inorganic chemistry, electrochemistry and environmental physical chemistry. He was appointed Extraordinary Professor at the University of Geneva in 2000. His current major research interests are twofold: (1) ion dynamics and electrokinetics of colloids, and (2) dynamic speciation and bioavailability of metals in environmental systems. He has published some 140 research papers, reviews and book chapters in these fields. He was chairman of the IUPAC Commission on Fundamental Environmental Chemistry from 1995 to 1999, and Chairman of the Electrochemistry Section of the Royal Dutch Chemical Society from 1993 to 2001. Together with J. Buffle, he edits the IUPAC Book Series on Analytical and Physical Chemistry of Environmental Systems, launched in 1992. Jacques Buffle is Professor Emeritus of analytical and environmental chemistry. He joined the staff of the Department of Inorganic, Analytical and Applied Chemistry of the University of Geneva, Switzerland, in the late sixties, and taught under- and postgraduate courses in analytical and environmental chemistry. Amongst many other cooperations, he has been also an Invited Professor at INRS-Eau, University of Quebec, Canada, for 20 years and Associate Professor of Electroanalytical Chemistry at the University of Lausanne, Switzerland. He was a member of the Division committee of IUPAC Division of Chemistry and the Environment, and a member of the Research Council of the Swiss National Foundation, from 1992 to 2000. He has authored about 260 research publications, 2 books, and is a co-editor of 5 other monographs. He is Series co-editor with H.P. van Leeuwen, of the IUPAC Series on Analytical and Physical Chemistry of Environmental Systems.