Already in the first generation of children born abroad to migrant parents, a language shift to the language of the host country and a loss of the heritage language frequently occurs. While some migrant parents talk to their children in their own mother tongues, a contrary scenario is no exception. In families including a Polish speaking parent or parents living in Germany, German frequently becomes the only language used for communication by members of the second generation. In other cases they become bilingual and are more or less able to alternate between both languages. This is sometimes accompanied by multiple ethnic and ethnolinguistic identifications. Which role does the heritage language play in the lives of Polish migrants’ children, and what does it depend on whether the interest and communicative competence in the heritage language are maintained beyond childhood? What are the relationships between competence in the heritage language, its usage, self-identity and, in particular, teenagers’ peer contact networks? Which other factors are of relevance? The book is devoted to the attitudes, competences and practices found among teenage children of Polish speaking mothers raised in Germany since birth or early childhood, with a consideration given to the impact from relevant Others and the impact of growing into adolescence. The competence in the Polish language in childhood may be followed by Polish dropping out of usage in the later period; this motivated the author to focus on teenagers rather than younger children. It is her position that while any period in one’s lifetime is important for its own sake, the gift of bilingualism is most precious if it is carried over into adulthood.