This chapter presents a cyclic model of interprofessional collaboration to support children in their transition from preschool to school. The conceptual model is based on activity theory and the concepts of expansive learning and boundary crossing. The expansive cycles of interprofessional teamwork are described as the connections between the team versus the collective and also as internalization versus externalization levels of activities. The process involves the following four expansive phases: 1. Selecting a problem of boundary work (the team, internalization)2. The analysis of systemic level contradictions (the collective, internalization)3. The development of new boundary-crossing forms of joint activities (the collective, externalization)4. Adapting these new actions to practice (the team, externalization)In this chapter, these phases of boundary work are outlined in a review of theory, earlier research findings and empirical data. Developmental intervention is the method through which expansive learning cycles are facilitated.