Silk comes from the cocoon of the silk worm. Although many insects produce silk, the commercial silk industry primarily uses the filament produced by the Bombyx mori or mulberry silk moth. The silk worm feeds on mulberry leaves and then attaches itself to a mulberry tree to spin a silk cocoon. This process takes from three to eight days and is referred to as pupating. Farmers raise the cocoons and sell them to manufacturers. Silk manufacturers sort cocoons according to color, size, shape and texture as these attributes affect the quality of the silk. Cocoons range from white and yellow to grayish. After the cocoons have been sorted, they need to be softened through a series of hot and cold immersions.