Studying complex systems has enormously changed our view of the world. The discovery that actions and reactions are often disproportionate and that small perturbations can cause tremendous responses, has led to new scientific disciplines such as catastrophe theory, chaos theory, and the theory of phase transitions. The behavior of complex systems is often dominated by their internal dynamics and hence only poorly controllable from outside. This has been addressed by the concepts of self-organisation and emergence. In many cases, a complex system can even evolve into one out of several (meta-)stable states, which is in clear contrast to linearly behaving systems with a unique solution. In addition, random perturbations, diversity (heterogeneity) in the properties of the individual system elements, network effects, time delays, and incomplete or uncertain information can lead to unexpected and sometimes paradoxical effects. The recently established European Complex Systems Society and the series of conferences under the title "European Conference on Complex Systems" has to be seen in this context. It aims at bringing together the various related disciplines, at focusing the diverse research activities, and at fostering them. The goals of this annual conference are to reflect the recent progress in the field of complexity science and to significantly increase the actively involved community. more on ECCS 2007 Dresden