The conception of this handbook goes way back, taking us more than five years until completion. It all began with an early plan to organize a symposium for the 31st International Congress of Psychology (ICP) for July 2016 in Yokohama, Japan. The intention was to bring together a group of international identity researchers, from within psychology and from neighboring disciplines, to see whether there were any new developments in identity theory and empirical research, and whether they had a common center or were drifting pieces moving in all kinds of directions (cf., for example, Nochi, 2016, or Watzlawik, 2016). This was the original idea. So, in the summer of 2015 we started contacting researchers we knew (and whom we did not know up to that moment), asking whether they would be interested in joining us for the symposium. Preparing the symposium was as stimulating as the actual gathering that took place on the afternoon of July 28 one year later under the header Identity and Identity Research in Psychology and Neighboring Disciplines. Janka Romero, the Commissioning Editor for Psychology at Cambridge University Press, had contacted us beforehand with the offer to talk about the potential to turn this into a book project, and we, the symposium participants, started following up the same night over dinner – not knowing that this would keep us busy for the next five years. We went through the usual editorial routines: developing a proposal, revising the proposal, and contacting old and new colleagues in the field, up to the point of delivering the full set of manuscripts in January 2021.