The aim of the research project "Populations and Policies in the Baltic Sea States" is to investigate determinants of population development in the Baltic Sea region. This involves various research fields such as family, work, health and migration, which requires a strong interdisciplinary framework: The project brings together researchers from the Max Planck Institute for Social Law and Social Policy in Munich and the Max Planck Institute for Demographic Research in Rostock who have backgrounds in demography, economics, epidemiology, public health, social policy and law. Both Max Planck Institutes have established a broad network of national and international research collaborations, particularly within the Baltic Sea region, and are internationally leading research centres in their fields.