This age saw the Greeks move towards larger cities and a reduction in the importance of the city-state. These larger cities were parts of the still larger Kingdoms of the Diadochi. Greeks, however, remained aware of their past, chiefly through the study of the works of Homer and the classical authors. An important factor in maintaining Greek identity was contact with barbarian (non-Greek) peoples, which was deepened in the new cosmopolitan environment of the multi-ethnic Hellenistic kingdoms. This led to a strong desire among Greeks to organize the transmission of the Hellenic paideia to the next generation. Greek science, technology and mathematics are generally considered to have reached their peak during the Hellenistic period.