The society, economy, settlement and culture of the territory of what is in the present-day the country of Estonia is studied mainly through archaeological sources. The era is seen to have been a period of rapid change. The Estonian peasant culture came into existence by the end of the Viking Age. The overall understanding of the Viking Age in Estonia is deemed to be fragmentary and superficial, because of the limited amount of surviving source material. The main sources for understanding the period are remains of the farms and fortresses of the era, cemeteries and a large amount of excavated objects.