The 'Communities of Tacit Knowledge' (TACK) ITN will focus on the concept of ‘tacit knowledge’ in architecture. Tacit knowledge is a specific type of knowledge that architects employ when designing, which is also embodied in the material vectors that they design with; from treatises and drawings to models and buildings. This ITN will train young researchers in the development of advanced theoretical frameworks and specialized methods for the analysis of the specific knowledge used by architects while designing buildings and cities. It focuses on the characteristics, the dissemination and the heuristic potential of this knowledge that is particular to architectural design practice. Structured around three training axes: (1) Approaching Tacit Knowledge: Identifying Methods and Histories, (2) Probing Tacit Knowledge: Concrete Cases and Approaches and (3) Situating Tacit Knowledge: Concepts and Theories, the TACK ITN for the first time combines the expertise on tacit knowledge that has been developed at ten different research centres in Europe. Together with three cultural and three practice-based partners, these ten research centres will train a group of scholars to explore and conceptualize the very character of tacit knowledge to better understand its possible roles in addressing new and pressing issues in the built environment from alternative vantage points. This powerful combination of expertise from industry and academia, will introduce these ESRs to new heuristic methods and add to their inter-sectoral employability. Implementation of the TACK ITN will result in ten PhDs, three online training modules, an international colloquium, a major exhibition, a lecture- and debate series, a synthetic reader, a book, and a website providing public access to research results and events.