This chapter introduces the topic of the book, social cash transfers for the poor in the global South, and depicts the research questions, theories, methods, indicators, and data of the analysis. The research questions relate to what kind of social cash transfer programmes have been set up in the global South, how international organizations came to accept the concept and constructed models of cash transfers, what factors made for the global spread of cash transfers, and if cash transfers have brought social citizenship to the poor. Drawing on Georg Simmel, T. H. Marshall, John W. Meyer, and Franz-Xaver Kaufmann, the theoretical approach of the book combines sociological theories of social policy, constructivist institutionalism, and world society theory, to complement the dominant approaches from welfare economics and political economy. Research includes qualitative and quantitative data and methods, with a unique large N data set. A figure depicts the research plan of the book.