The research school ICS pursues a coherent overarching research program on the nature and dynamics of Social Networks, Solidarity, and Inequality. The aim is to model and explain how social networks affect, and are affected by, solidarity and inequality in different social settings. People strive for private goals, but need to contribute private resources for common ends without direct compensation for such contributions. This tension creates social dilemmas or ?level paradoxes?: strategies that are rational at the level of the individual can lead to unintended or suboptimal outcomes at group or society level, thereby creating solidarity and inequality problems. The ICS likewise maintains a graduate research training program for research master students and PhD students. This overarching research program is closely tied to the graduate research training program. The training program provides a broad set of research and training options for graduate students, while at the same time ensuring guidance, support, and intensive supervision. The graduate research training program includes four sociology/social science research master programs as they are realized under the responsibility of the Graduate Schools of Social (and Behavioral) Sciences at the universities of Groningen, Nijmegen, and Utrecht. The integration of theory formation, methodologically advanced empirical research, and state of the art statistical modeling is a core feature of the research program and of graduate training. The program explicitly aims at solving sociological and social science problems and wishes to contribute to the advancement and growth of theoretical and empirical knowledge in sociology and social science. The program aims at high quality research in its field, on a par with internationally leading research groups. Research master students and PhD students are trained in year-groups, allowing for systematic and rigorous feedback on how theory and methods should be applied to specific or new areas of research under the common theme. The common theme are problems of social solidarity. Solidarity problems are directly related to an overarching problem studied by sociology and social science: the problem of social coordination, cooperation, and cohesion. Solidarity problems are studied in informal settings such as families, ethnic groups, and neighborhoods, and in formal settings, such as relations within and between formal organizations. The common approach in theory building is structural individualism. Social phenomena are thereby explained as results of purposive behavior of individuals and of corporate social actors. While behavior is purposive, results of behavior are often unintended. Purposive behavior is shaped by constraints and opportunities posed by social and institutional contexts, including ties and interdependencies between actors. The so-called ?macro-micro-macro question? guides theory building: this helps to avoid a reduction of social science to the perfect market model of neoclassical economics or the over-socialized conception of human beings in traditional sociology. Common methods are applied in empirical testing of theories and hypotheses. Structural individualism implies that data sets comprise individual as well as contextual information. Accordingly, ICS researchers play a key role in the collection of multi-actor, multi-level, and multi-event data sets, including: (a) information about the actors and their interdependence with respect to constraints, actions, and outcomes, (b) information about the various levels of aggregation (individual, various types of context), and (c) information about multiple events over time that can provide information on how later events are conditioned by earlier ones. Different and complementary kinds of data are employed, including not only large-scale survey data, but also, for example, historical data and archival data, experiments, and data from case studies. Employing complex data sets for testing hypotheses requires, in turn, appropriate statistical models that mathematically express the main theoretical relations between the observed variables bearing on the various actors, levels, and events. The ICS actively contributes to the further development of such models.