Greek scholars in the Renaissance
The migration waves of Byzantine Greek scholars and émigrés in the period following the end of the Byzantine Empire in 1453 are considered by many scholars key to the revival of Greek studies that led to the development of Renaissance humanism and science. These émigrés brought to Western Europe the relatively well-preserved remnants and accumulated knowledge of their own (Greek) civilization, which had mostly not survived the Early Middle Ages in the West.
Source: Wikipedia — Greek scholars in the Renaissance (CC BY-SA 4.0)