Cotton is cool: wool is warm. They're practical. But silk? Silk is soft, it is smooth, it is sophisticated-the queen of textiles. It is also possibly the most expensive material in the world, and indeed in ancient Rome it was more expensive than gold. But it is strong as well a thread of silk is stronger than steel. I wanted to discover more about this mysterious material, so I decided to go to China. China is where the secret of silk was discovered more than 4,000 years ago, and today it is still the biggest producer of silk in the world. The first person I visited was Shen Congwen, advisor on ancient textiles to the Palace Museum in Beijing. He showed kme some silk that workers found in a tomb in Jianglin, in Hubei Province. It was more than 2,000 years old but still beautiful. He told me that he thinks these old silks are more beautiful than modern silks. In ancient times, weaving was done from the heart. In modern times, weaving is done for commerce: So, how do you make silk? The first problem is that the silkworm only eats leaves from one tree-the mulberry tree.