Science has developed immensely over the last century. For example, in addressing a wider and wider range of topics, and requiring more and more resources, scientific research has become increasingly collaborative and interdisciplinary. In this talk, I shall analyze some of the epistemic implications of this development. I shall focus on how groups of different kinds and different sizes can provide different conditions for collective knowledge production, and I shall discuss how philosophical analyses of knowledge production in groups can provide input for ongoing debates in science policy on research organization, research funding, and strategic research planning.