In vitro models—cells that are cultured outside the body, and studied as models of living organs or organisms—have been increasing their importance in a wide range of fields in biology and medicine. Yet they involve epistemic problems. How can simplified and experimentally modified cell culture systems serve as reliable models of living organs and organisms? How do they function in broader inferential practices in different contexts? How do experts of different fields, who have different aims and values, interact and collaborate to generate, study, and use in vitro models? This project will assess the prospects and limitations of in vitro models in comparative biology through answering the above questions. It will integrate philosophical analysis and empirical qualitative methods to examine a case study: in vitro comparative primatology. This is a rapidly developing interdisciplinary area of research, which studies different primate species by applying advance in vitro technology to serve research into human evolution, veterinary science, conservation, etc. Using this case study, this project will generate novel insights into how various experimental modifications, inferential practices, and social/institutional factors facilitate and/or constrain representational function of scientific models. This project will benefit from and contribute to the existing expertise at the Section for History and Philosophy of Science at the University of Copenhagen, which hosts and participates in research projects that examine epistemic and social implications of specific practices of biomedical research, including in vitro models by combining philosophical analysis and qualitative methods.