Silk is a fiber produced by spiders and caterpillars. The most usual silk is the one produced by Bómbix mori (who eats only mulberry tree leaves); althought there are another silk caterpillars, such as tussah worms (which produces the "tussah silk" or wild silk), wild silk worms who live naturally in tropical or semi-tropical forests, eating all kinds of different trees.

    Silk is the smoothest and brightest natural fabric. It is not a good electricity and heat carrier, and it is powerful, elastic, long lasting and resistant to dirt and odours. It also makes it less likely than other fabrics to cause allergic reactions or skin abrasions.

    Silk absorbs moisture away from skin, which makes it cool in the summer and warm in the winter. Pure silk helps to preserve heat in extreme moisture and cold conditions: this is the reason why it is used as underwear in climbing and sleeping bags production.

    Silkworm breeding was the reason which caused Chine to have the silk monopoly during millenniums, although Europe imported silk breeding or sericulture. At present time, China and Japan are the main world-wide suppliers, but, in between, Silk Road was of high importance.