This chapter begins with contemporary experiences of migration and the resulting transculturality in order to underline the complete foreignness of medieval concepts of migration and transculturality. It outlines a number of terms from the vantage point of medieval studies. The chapter presents research in the fields of migration and transculturality focused on the concepts and perceptions of the Middle Ages. It shows how medieval perceptions and judgements changed with regard to the intermingling of peoples and cultures. Cultural memories during the Early and High Middle Ages were based on the secure knowledge that the entire existing order relied on immigration, change and cultural breaks. The condition for the new European order at the turn from Antiquity to the Middle Ages was thus the complete restructuring of all previous social orders and quotidian certainties. Alterity has become virtually the new key concept for historical studies. Yet, while ethnologists essentially study synchronous alterity in non-Western contexts, historians find their alterities.