In this volume, as the title indicates, the focus is on understanding and elaborating what might be said to be "going on" in supervision as well as further exploring what is distinctive about systemic supervision. Looking at processes within systemic supervision involves engaging with the different contexts within which the supervision takes place and engaging with a range of theories - some developed or applied within therapeutic contexts and others drawn from theories of learning. Various theoretical frameworks have emerged and been described as underpinnings for systemic supervision. Social constructionist and narrative ideas have been vital in the creation of supervisory practices that promote open dialogues, multiple perspectives and the interrogation of traditional assumptions about expertise and hierarchy. This has inevitably led to a discussion of tensions and contradictions: unease about implicit practices of power, the problematics of assessment and evaluation and issues concerning the allocation of clinical responsibility. Positioning theory, dialogic theories and ideas from the field of adult education have also contributed helpful theoretical concepts for use by systemic supervisors.