The volume summarizes research on the structural convergence and divergence of languages in the eastern part of the Circum-Baltic Area by providing its profile against a genealogical and typological background. Methodological issues needed to assess factors that condition convergence in contact superposition zones, or that otherwise lead to differentiation among related varieties, are discussed. Against this backdrop synthetic surveys of major and minor Finnic languages are provided, followed by corpus-based case studies on morphosyntactic phenomena. The volume thus presents both a synthetic compendium and a series of specific up-to-date studies, with special attention to micro-variation.