In this paper, I aim to explore the relationship between the composition of project collectives, the division of labor within research projects and the knowledge production based on field research in ERC funded projects (2014-2020). These projects have short-term fundings but can also be used to fund long-term teams and research. In that sense, they offer many ways to construct research collectives and, as such, different kind of division of labor. They are however mostly hierarchical because ERC fundings are individual grants. The projects studied are selected for the fact that they study specific spaces. Most of the time, they imply fieldwork, and team members are hired in relation with it. The field site choice and the nature of the fieldwork influence the composition of the research collective and the role assigned to each member and vice versa. My presentation focuses on this interaction and is based on the analysis of twenty interviews conducted with principal investigators and participant of ERC projects from different countries and disciplines, and working on various spaces. Firstly I will present the different ways of constructing a research collective among ERC projects, taking into account the status, the unclear boundaries of the research teams and the previous knowledge or not of all the members. Then, I will analyse the mutual influence between the research collectives and the field site and fieldwork, and the modifications that can occur during the project. Finally, I will explore the consequences of these interactions in terms of knowledge production.