In this issue of Medical Education, Nathan Hodson 1 discusses 'landscapes of practice,' a sociocultural theory of learning proposed by Wenger-Trayner et al. 2 Landscapes of practice theory is an extension of the frequently cited communities of practice theory and describes how learners traverse landscapes comprised of multiple communities of practice, and in the process cross boundaries, acquire knowledge and develop professional identities. Hodson 1 points to the imperative inherent in landscapes of practice: that learners spend time at community boundaries to enhance their own learning and, in turn, to enrich their communities. In this commentary, we consider how the boundary experiences of residents in clinical workplaces might shape learning and professional identity formation.In medical education, great emphasis is placed on creating positive learning environments to support residents' learning through work. Ideas about what constitutes an ideal clinical learning environment typically draw on communities of practice theory and related sociocultural theories of learning, referencing opportunities to connect with senior community members, to participate in community practices and to be valued as community members. If we consider the resident's pathway through the lens of landscapes of practice theory, we can see that not only clinical learning environments within communities, but also those at the boundaries between communities, at which residents spend much of their time, are critical to their learning.As instantly relatable as communities of practice theory was to workplace learning in medical education, so too does the concept of landscapes of practice make intuitive sense when we think about residents' learning trajectories. The rotational system of clinical education, in which residents move at regular intervals between clinical teams, specialties and sites, is one that propels learners through a constellation of related communities, or practices. Together, these communities and their corresponding domains of knowledge comprise the curriculum of postgraduate medical education. Residents experience a series of short-lived community memberships, during which they inhabit the peripheries of their communities. With each change in clinical team or specialty, they renegotiate their understanding of the distinct culture and practices of a new community. In doing so residents become capable, useful community members. Such transitions have been identified as critically intensive learning periods, requiring recognition and support within communities. 3 Professional identities are formed in the negotiation of these boundary crossings as learners accumulate bodies of knowledge relevant to the landscapes they traverse. These include an ability to adapt to new environments and styles of practice, greater comfort with stressful situations, better organisational and decision-making skills and flexibility. 4 Thus, learners develop knowledgeability, the capacity to bring the relevant practical knowledge to situations in pr...