As is true for all natural fibres, the quality of the raw silk determines the quality of the final product. Silk begins with the cocoon. Different silk worms produce different types and qualities of cocoons, and thereby different silks. Premier among them is mulberry silk, produced by bombyx mori, the mulberry silk worm. This silk is considered the best because of its white colour, sheen, fineness and evenness of fibre. The name derives from the plant eaten by the silk worm: the mulberry tree, whose freshly picked leaves are the only foodstuff these silk worms accept.