Decoction is a method of extraction by boiling herbal or plant material to dissolve the chemicals of the material. It is the most common preparation method in various herbal medicine systems. Decoction involves first drying the plant material; then mashing, slicing, or cutting the material to allow for maximum dissolution; and finally boiling in water to extract oils, volatile organic compounds and other various chemical substances. Occasionally, aqueous ethanol or glycerol may be used instead of water.