The importance of knowledge sharing for modern organizations is widely acknowledged. However, we know little about the micro-processes of knowledge sharing and its contribution to the work practices of organization members. In order to open the black box of knowledge sharing, two field studies were undertaken within industrial research organizations. Informed by speech act theory and the interpretation of research work as problem solving, the empirical studies yielded taxonomies of knowledge sharing moves and the effects of knowledge sharing. Taken together, these taxonomies show the heterogeneity of the process and value of knowledge sharing. Furthermore, the paper contributes to the nascent study of the justification of organizational knowledge by showing the different roles of moves in the development of justified solutions. Finally, the paper discusses the facilitation of the different types of knowledge sharing.