How can complex systems approach enrich behavioural and social science research, and increase its relevance to public policy? The symposium will shed light on various ways of how theoretical insights and empirical methods of complexity science can contribute to research and practice of interventions to change behaviour in various societal domains. We have both international and Finnish speakers who are experts in this area. All scholars, students and audiences interested in the behaviour change research and policy are welcome to discuss and seek promising avenues for the future!