Animal fats are lipids derived from animals which are used by the animal for a multitude of functions, or can be used by humans for dietary, sanitary, and cosmetic purposes. Depending on the temperature of the fat, it can change between a solid state and a liquid (oil) state. Chemically, both fats and oils are composed of triglycerides. Although many animal parts and secretions may yield oil, in commercial practice, oil is extracted primarily from rendered tissue fats from livestock animals like pigs, chickens and cows. Dairy products yield animal fat and oil products such as butter.