||This thesis presents an ethnography of a research institute in biology and biomedicine (Institut de Biologia i Biomedicina, UAB). As such, it intends to contribute to the tradition of Studies of Science and Technology (STS), in particular, to the so-called «laboratory studies». Likewise, on dealing with technoscience it also attaches to an emergent discipline, social psychology of science and technology. Theoretically, this work tackles the notion of 'belonging', offering alternative ways of imagining 'relationality' or 'being together'. To do so, we find inspiration in the notion of 'partial connection', as elaborated by Strathern, as well as in several contributions from social sciences, mainly anthropology and STS. Belonging, we argue, does not mean to be included in clear-cut categories, as if communities were enclosed by a symbolic boundary that reproduces reification and exclusion. On the contrary, belonging is an on-going process open to the relation. When we enter a relationship with alterity, the certainties of our world shake, clear-cut categories and identities are suspended, and we question our own position. We are not inside or outside the boundary, but in an ambiguous space between borders -we inhabit the boundary, we find ourselves in a liminal moment of ontological transformation. Thinking 'belonging' from within liminality allows us to understand how heterogeneous entities can nevertheless attach together and belong to each other. Each chapter of the thesis tests differently the empirical productivity of these ideas. Firstly, the thesis presents some of the transformations that the author suffers, on relating to the community offering hospitality. Moved by something other than herself, the ethnographer emerges out of this encounter as a new position partially connected to the old one: partly the same, partly different. Thus, self-other relations involve a vector of movement, of exile, of expropriation typical of liminal situations. Next, the structure, functioning, rituals and institutional character of a scientific group in the context of Spanish University are analysed. The work describes the progressive constitution of scientists as competent members of their labs, the development of their careers from students to leaders. We also discuss the ambiguous role that the latter play when looking for funding for the group, developing an heterogeneous activity in which the boundary between 'science' and 'politics' blurs. Likewise, we show how scientists in this country try to overcome some limitiations of Spanish science (for instance, low budget) through collaborations and other original strategies, in order to assure their belonging to European and international science. In an attempt to extend the notion of relationality to materials, the thesis approaches how scientists connect and articulate the diverse results which different groups achieve locally, so as to construct collectively a common universe. To this aim, and observing some collaborative work between laboratories, we will analyse how a protein is articulated and engineered into being. The thesis also deals with several tensions that cross the IBB and its knowledge production, such as those between national science and international science, market and gift economy, exchange and collaboration, territorialisation and deterritorialisation, virtuality and actuality, stability and mobility. These tensions are examined not to create antagonisms or reify dichotomies, but to show how the IBB is constituted precisely in the creative, moving field defined by all of them, as a complicated assemblage that brings together parts which do not quite fit. To describe the work of constitution of such an assemblage, we inquire into the notions of exchange, mediation and movement, as well as into their bonding characteristics. At last, the conclusion will try to summarise and blend the different concerns that are elaborated in the whole work.