This proposal outlines a highly ambitious and path-breaking research program. Through a tightly integrated package of basic theoretical work, strategic empirical research projects, international workshops, and a large number of publications in leading journals, the research program seeks to move sociology in a more analytical direction. One part of the research program focuses on the epistemological and methodological foundations of analytical sociology, an approach to sociological theory and research that currently receives considerable attention in the international scholarly community. This work will be organized around two core themes: (1) the principles of mechanism-based explanations and (2) the micro-macro link. The empirical research analyzes in great detail the ethnic, gender, and socio-economic segregation of key interaction domains in Sweden using the approach of analytical sociology. The interaction domains focused upon are schools, workplaces and neighborhoods; domains where people spend a considerable part of their time, where much of the social interaction between people takes place, where identities are formed, and where important resources are distributed. Large-scale longitudinal micro data on the entire Swedish population, unique longitudinal data on social networks within school classes, and various agent-based simulation techniques, are used to better understand the processes through which schools, workplaces and neighborhoods become segregated along various dimensions, how the domains interact with one another, and how the structure and extent of segregation affects diverse social and economic outcomes.