The majority of pet owners in the United States feed their companion animals commercially prepared pet foods. These products are available in several forms that vary according to the processing methods used, the ingredients included, and the methods of preservation. Foods can also be categorized according to their nutrient content, the purpose for which they are formulated, and the quality of ingredients they contain. One of the broadest classifications of commercial pet foods divides products according to processing method, methods of preservation, and moisture content; these categories are the dry, wet, and semimoist foods. In recent years, a variety of foods have been developed to meet specific needs of some pet owners. These include natural and organic foods, raw food diets, and vegetarian products.