The period is named after the neighborhood of Tokyo where archaeologists first uncovered artifacts and features from that era. Distinguishing characteristics of the Yayoi period include the appearance of new Yayoi pottery styles and the start of an intensive rice agriculture in paddy fields. A hierarchical social class structure dates from this period and has its origin in China. Techniques in metallurgy based on the use of bronze and iron were also introduced from China via Korea to Japan in this period.