The book contains collected and scientifically systematized material on two large ethnic groups - Finno-Ugric and Balts, who inhabited significant areas of North-Eastern Europe in the Middle Ages - from the coast of the Baltic Sea in the west to the Ob basin in the east. The study is based on thousands of archaeological sites and huge clothing material obtained as a result of excavation work for more than 150 years. Written sources and data from related sciences are widely used. The result of the study is a reconstruction of the specific history of each of the Finno-Ugric and Baltic tribes of the early Middle Ages and the conditions for the formation of medieval nationalities. Settlements, dwellings, life and economy are characterized in detail, as well as social relations, customs and beliefs of medieval tribal formations of Finno-Ugric and Balts.