This book investigates how collaborative scientific practice yields scientific knowledge. At a time when most of today's scientific knowledge is created in research groups, the author reconsiders the social character of science to address the question of whether collaboratively created knowledge should be considered as collective achievement, and if so, in which sense. Combining philosophical analysis with qualitative empirical inquiry, this book provides a comparative case study of mono- and interdisciplinary research groups, offering insight into the day-to-day practice of scientists. The book includes field observations and interviews with scientists to present an empirically-grounded perspective on much-debated questions concerning research groups' division of labor, relations of epistemic dependence and trust.