The discourse on the connection between design and social innovation is today rich and animated: after a decade since its beginning, we can detect signals of maturity that are also widely reflected in several research programs recently funded by the European Commission. This chapter presents a conceptual framework, drawn from diverse applied research projects in design for social innovation, analysed through the lenses of some of the most debated theoretical approaches around design, innovation and social issues in the broadest sense. The research projects here considered come from the experience of the POLIMI DESIS lab, the Politecnico di Milano based design team belonging to the international DESIS Network (Design for Social Innovatio...