The core process of complexity, self-organisation, requires a system that is open and far from equilibrium, with ill-defined boundaries and a large number of non-linear interactions involving short-loop feedback. In such a system, knowledge does not exist objectively 'out there'; rather, it exists as a result of the exchange between participants, an action that becomes knowing. Understanding is placed between participants rather than being contained in one or the other. Knowledge is not constructed separately in the mind of the knower, but, rather, it emerges; it is co-created during the exchange in an authentic recursive transactive process. Learning and knowing become adaptive responses to continuously evolving circumstances. An approach to curriculum based on self-organisation is characterised as rich, recursive, relational and rigorous and it illuminates how a curriculum can be understood as a complex adaptive system. The perspective of complexity applied to medical education broadens and enriches research questions relevant to health professions education. It focuses our attention onto how we are together as human beings. How we respond to and frame the issues of learning and understanding that challenge contemporary medicine and, by extension, medical education, in a complex and rapidly changing world can have profound effects on the preparedness of tomorrow's health professionals and their impact on society.