A substantial body of literature has recently been concerned with the structure and dynamics of the collaboration networks that underlie the production and dissemination of scientific knowledge. Despite the growing interest in these networks, relatively little emphasis has been placed on two broad areas of investigation: on the one hand, the interplay of the growth mechanisms underpinning the evolution of collaborative arrangements; on the other, the implications that the structure and multiplexity of these arrangements have on knowledge creation and diffusion. The articles in this Special Issue aim to bridge these gaps in the literature and, by embracing a variety of perspectives, contribute towards a better understanding of how collaboration networks originate, function, and evolve. This Introduction offers a theoretical and methodological framework for the articles here included. It begins by discussing problems of measurement of scientific collaboration, and goes on to examine the role that growth mechanisms, structural variety and multiplexity play in shaping the genesis and functioning of collaboration networks. In reviewing current and emerging research themes, the discussion will also identify promising research directions that will stimulate future work on collaboration networks in science and technology.