Cheese is a dairy food made by coagulating milk, usually with rennet or an acid, and separating the resulting curds from the liquid whey. It has been made from the milk of cows, goats, sheep, and buffalo for thousands of years; the earliest known cheese-making evidence dates to about 5500 BCE, from residue found in pottery strainers in Poland. Cheeses vary widely in texture and flavor depending on the milk, culture, and aging used, ranging from soft and mild, like brie or fresh mozzarella, to hard and sharp, like aged cheddar or Parmesan.