Silk is a continuous protein fiber (filament), which is spun by silkworms in nature and is formed as an egg-shaped object (cocoon) along 30 days time, which frequently includes feeding from mulberry tree leaves and sleeping, silkworms finally began to produce silk fibers from their salivary glands and they cover these two fibers using a layer of resin. Cocoon has a long and continuous fiber with a length between 800 to 1200 meters
- After completion of spinning cocoon around itself, silkworm fall sleep (pupa); then, after becoming Butterfly (Moth), it drills cocoon and gets out of it. In a few days, Moth starts mating and egg laying (eggs); after that its life goes end.
- The silk fiber production process starts by human factor after production of cocoon by silkworm and before conversion of pupa to butterfly.