Well, silk, for starters. For millennia, silk was only produced in China. It is spun from the cocoons of mulberry tree-eating worms, and the process of silk making, as well as the techniques for raising the worms, were closely guarded secrets since the lion's share of China's wealth came from silk production. The Chinese used silk as fishing line, to buy off nomadic raiders to keep things peaceful, and to write before they invented paper. But as an export, silk was mostly used for clothes. Silk clothing feels light in the summer and warm in the winter, and until we invented $700 pre-distress designer jeans, decking yourself out in silk was the number one way to show people that you were wealthy. Thanks, Thought Bubble.