Romualdo Pastor-Satorras got his PhD at the University of Barcelona. He has been research fellow at Yale University and research assistant at the Massachusetts Institute of Technology in Boston. He spent two years as a research fellow at the International Center for Theoretical Physics (UNESCO) and then moved back to Spain in 2000 as Assistant Professor at the University of Barcelona. Since 2001, Pastor-Satorras has been research scientist and lecturer at the Universitat Politecnica de Catalunya. He is the author of more than 40 research papers in different areas of non-equilibrium statistical physics, condensed matter theory and complex systems analysis. Alessandro Vespignani obtained his PhD at the University of Rome 'La Sapienza'. After holding research positions at Yale and Leiden University, he joined the condensed matter research group at the International Center for Theoretical Physics (UNESCO) in Trieste. He has authored more than 100 scientific papers on the statistical physics of non-equilibrium phenomena, critical phase transitions and complex and disordered systems. At present he is senior research scientist of the CNRS, at the Universite de Paris-Sud, France.