Silk is a fibre most commonly formed from proteins secreted by Bombyx mori, a Silkworm. These silkworms are actually mulberry tree moth caterpillars, and it is the female moths which lay eggs that then hatch into larva. It's these larva that secrete a fluid high in protein and forms a continuous thread which is repeatedly wound to create a cocoon. The silk cocoon is placed in hot water to loosen the thread, which is then wound onto wheels. Once the raw silk has been wound, it can be spun into a variety of different types of thread depending on its intended use.