Though for once China was under foreign rule, the Yuan Dynasty evolved one of the greatest innovations of all time, paper money. For context, the supply of precious metals, namely copper, prevented expansion of foreign trade, which was essential for the Mongols. Even if they expanded copper production, mammoth proportions were used to create religious objects like statues. Paper money was first issued by the Song, but it was used too rarely used to develop trade. Under the Yuan Dynasty, paper money became the sole currency, helping the growth of trade. In conclusion, the Yuan Dynasty, though foreign rulers, innovated paper money, shaking the world both throughout the dynasty and
