Créplet, F.Dupouët, O.Vaast, E.2017-04-152017-04-152003978-94-017-0115-0This paper explores the different social structures coexisting within a biology laboratory. This work draws upon an empirical study and the results are analysed using the social network analysis toolbox. We evidence that actors form links between them in order to carry out cognitive activities. Depending on the content of this activity, resulting networks can take different shapes. When dealing with scientific knowledge, actors tend to form an epistemic community, whereas they form a community of practice when they seek to enhance their skills in setting experiments. Moreover, these two structures are connected by means of boundary objects and boundary spanners.enText10.1007/978-94-017-0115-0_3