The book „Social, emotional and intercultural competencies for inclusive school environments across Europe: Relationships matter“ brings in the insights from the three-year learning process of the HAND in HAND: Social and Emotional Skills for Tolerant and Non-discriminative Societies Erasmus K3 policy experimentation project that targeted the need detected in Europe and internationally to develop inclusive societies (schools and classrooms) that allow every student to feel accepted and be able to achieve their potential, particularly in response to increasing migration trends. HAND in HAND seeks to achieve this by fostering the social, emotional and intercultural/transcultural competencies of students and school staff in the whole-school approach. The list of fundamental questions the monograph deals with are: What are social, emotional and intercultural/transcultural competencies? How do we promote them in schools? What outcomes do we expect on the individual, classroom and school level? How do we measure them and how do we evaluate the expected effects? How to assure high-quality implementation and transferability across contexts? How are these competencies established on a system level and which areas are deficient? The monograph addresses these questions, one by one, providing a holistic overview of social, emotional and intercultural/transcultural competencies that moves beyond the borders of a specific project