A meatball is a ball of ground meat where the meat is rolled into a ball along with other ingredients, such as bread or breadcrumbs, minced onion, various spices, and possibly eggs, rolled together by hand, and cooked by frying, baking, steaming, or braising in sauce. There are many kinds of meatball recipes using different kinds of meats and spices. While some meatballs are mostly made of meat and ingredients to cement the ball, others may include other ingredients. How one makes meatballs depends as much on one's cultural background as on individual taste. There are even "meatless" meatballs to satisfy vegetarian palates. From the Balkans to India, there is a large variety of meatballs in the kofta family. The ancient Roman cookbook Apicius included many meatball-type recipes. Cooking is the process of preparing food by applying heat, selecting, measuring and combining of ingredients in an ordered procedure for producing safe and edible food. The process encompasses a vast range of methods, tools and combinations of ingredients to alter the flavor, appearance, texture, or digestibility of food. Factors affecting the final outcome include the variability of ingredients, ambient conditions, tools, and the skill of the individual doing the actual cooking. The diversity of cooking worldwide is a reflection of the aesthetic, agricultural, economic, cultural, social and religious diversity throughout the nations, races, creeds and tribes across the globe. Applying heat to a food usually, though not always, chemically transforms it, thus changing its flavor, texture, consistency, appearance, and nutritional properties. Methods of cooking that involve the boiling of liquid in a receptacle have been practised at least since the 10th millennium BC, with the introduction of pottery.