“You will hold in your hands the proceedings of the last conference ever on integral-field spectroscopy.” So the daring statement that we, organizers, made at the end of an extremely interesting and busy week of conference in October 2005. Indeed, the quality and diversity of the contributions in this book indicated that integral-field spectroscopy had evolved into a mature technique. Future books would not be dedicated to the technique as such but to the science achieved with ‘3D-spectroscopy,’ that is a dedicated book after thisone,assemblingscienceresultsacrosssomanyfields,isunlikelytoappear again (or have you seen a proceeding dedicated to ‘long-lit spectroscopy’ recently?). In a sense this is very encouraging. The idea of this conference was an offspringof theResearchandTrainingNetwork(RTN)‘Euro3D’sponsoredby the European Commission. The goal of this network was to promote integr- field spectroscopy from an technique for experts to a common user utility for astronomical research. When we first talked about this conference the VLT, for example, was not yet equipped with any integral-field spectrograph. We were wondering whether anyone would actually attend the conference in 4 years’ time and would have anything to report upon. We were rewarded for our optimism and very positively surprised about the progress made in the years after that. A progress, of course, driven by theadventofsomanyintegral-fieldspectrographsaroundtheworld,installed on 4m to 8–10m class telescopes. Many of these instruments are referred to in the present book. Yet, this is explicitly not a book dedicated to technical issues,butfocusingonthescience.Thus,thenameof theconference,Science Perspectives for 3D Spectroscopy.