One of the interesting things about the Nishijin Textile Center (西陣織会館) for the lovers of silk, is that you can see the different stages of the development of the silk worm to harvesting the silk tread. You can see the silk being woven and the lady who does it will also give you an explanation in English.
The cocoon is made of a thread of raw silk from 300 to about 900 meters (1,000 to 3,000 feet) long. The fibers are very fine and lustrous, about 10 micrometers (1/2,500th of an inch) in diameter. About 2,000 to 3,000 cocoons are required to make a pound of silk (≈0,4 kg).