In the post-industrial period restrictive migration policies, though once virtually absent in the industrial era, have taken on extreme importance. Widespread dissatisfaction with the pull-push framework and neoclassical economic explanations of the causes behind migration has initiated a serious of new, exciting theoretical approaches such as: new economics of labour migration, dual labour market theory and world system theory, migrants’ network theory. Flows of people between the countries belonging to one migratory system occur within a national context whose policy, economic, technological, and social dimensions are constantly changing, partly in response to the feedback and adjustments that stem from the migration itself. In the late 1980s and early 1990s, the opening of Central and Eastern Europe borders and the disintegration of the former Soviet Union and Yugoslavia fundamentally changed the pattern of migration in the region. The chapter also presents an overview of the key concepts discussed in this book.