It was with great dismay that we heard the sudden and much too early death of our beloved colleague Arren Bar-Even. The scientific work of our Max Planck Research Network for Synthetic Biology (MaxSynBio) is closely related to the research of Arren Bar-Even, and many colleagues in our network have worked with him. His work in the field of synthetic biology and especially in the field of metabolic networks has moved frontiers and has been recognized worldwide. His sudden death leaves a huge gap in the scientific community that will be difficult to fill. However, we will miss Arren Bar-Even not only as an outstanding scientist, but also as a sympathetic colleague. Arren's enthusiasm, charm and humour will remain unforgettable. We would like to express our special sympathy to his scientific and personal family. Jakob Schweizer on behalf of MaxSynBio and its spokesperson Kai Sundmacher