PURPOSE: Participating in clinical practice shapes students' identities, but it is unclear how students build meaningful relationships while "dipping into" various social contexts. This study explored with whom students interacted, which social relationships they built, and how these relationships contributed to the formation of a professional identity. METHOD: In this longitudinal study at University Medical Center Groningen, University of Groningen, the Netherlands, 9 undergraduate medical students recorded experiences of thinking about themselves as future professionals (September 2015 to March 2017). The authors conducted template analysis using both open coding and a priori themes derived from Wenger's modes of belonging to communities of practice: engagement, imagination, and alignment. RESULTS: The authors received 205 recorded experiences. While rotating, students used engagement, imagination, and alignment to give meaning to clinical workplace social interactions. Participants considered relationships with doctors, patients, and peers as preconditions for engaging in meaningful experiences. Although imagination and alignment were less represented, discussing imagination with peers and physicians stimulated a deeper understanding of what it means to become a physician. Explicitly being invited "to the table" and awareness of the benefits of being a clerk were instances of alignment that stimulated the development of identities as future doctors. CONCLUSIONS: To understand the nature of professional identity formation, Wenger's modes of belonging must be considered. Where engagement is very prevalent, imagination and alignment are less spontaneously mentioned and therefore more difficult to foster. Looking for ways to support imagination and alignment is important for students' sensemaking process of becoming a doctor.