This paper gives an overview of important studies and research works in the Ruhr Area and surroundings regions dealing with (plurilingual) language acquisition and the maintenance of heritage languages. Whereas former studies mainly focused on the acquisition of German as a second or foreign language, nowadays research also considers bilingual acquisition, i.e. German and the minority language. Nevertheless, the overview highlights that (a) many existing language pairs have not yet been analysed yet (e.g. German-Turkish or German- Polish), and (b) that institutions such as kindergartens or schools still only focus on German and not on the promotion of multilingualism. In this overview, it becomes clear that the University of Duisburg-Essen played a decisive role in assessing the interest on the study of plurilingual language acquisition.