Students in higher professionals education are prepared for high level professional practice. To be able to fulfill their future roles, their educational programmes provide them interaction with professional knowledge, theoretical knowledge and professional practice. These types of interactions are presumed to aid students in their transformation from high school student to a professional in a complex society. However, it still is unknown how the different types of knowledge interact in the transformation of students to professionals through higher professional education, as well as the prerogatives for this interaction. This longitudinal study will follow 4x25 students of four different applied disciplines during their four years of undergraduate education to better understand this role of knowledge. In a mixed-methods design the interaction between the development of their professional identity, professional knowledge-base and notions of just professional action will be investigated. This poster presents an overview of the research design.