Rudiger Hell studied Biology at the Technical University of Darmstadt, Germany, and completed his PhD at the University of Cologne, Germany in 1989. From 1990 to 1992 he worked at the University of California in Berkeley as a postdoctoral researcher. After returning to Germany he completed his postdoctoral thesis at the University of Bochum in 1998 and held a position at the Leibniz Institute for Plant Genetics and Crop Plant Research in Gatersleben. During that time he developed his ongoing interest in molecular mechanisms of plant nutrition, especially sulfur metabolism and cellular redox control. In 2003 he was appointed chair at the Heidelberg Institute for Plant Sciences. He served as Dean of the Faculty of Biosciences at Heidelberg University from 2005-2007, and is currently the managing director of the university's Plant Sciences Institute. Ralf R. Mendel studied biochemistry at the Humboldt University in Berlin, completed his PhD at the Martin-Luther-University Halle in 1979 and his postdoctoral thesis in 1985. During that time he held a position at the Institute for Plant Genetics and Crop Plant Research in Gatersleben. In 1992 he was appointed Full Professor of Botany at the (now) Institute of Plant Biology of the Braunschweig University of Technology, Germany. He has been the director of the Institute since 1993 and also served as Dean of Biosciences at Braunschweig from 1997 to 1999. His research focuses on the cell biology and biochemistry of molybdenum in plants and humans.