Cheese, a traditional food incorporated into many cuisines, is used as an ingredient in cooking or consumed directly as an appetizer or dessert, often with wine or other suitable beverages. Great numbers of cheese varieties are produced, reflecting in part the versatility of the microorganisms used in cheese-making that this FAQ report will describe. Cheese is one of the few foods we eat that contains extraordinarily high numbers of living, metabolizing microbes, leading some participants to say, "Cheese is alive!" The broad groups of cheese-making microbes include many varieties of bacteria, yeast and filamentous fungi (molds). This report focuses on the microbiology of "natural" cheeses, those made directly from milk, including hard and soft varieties such as cheddar, mozzarella and camembert.