You might find these in a grocery store, but more likely you'll have to order it online from a cheese-making supply store. For this recipe and most other cheeses, use any mesophilic culture. These bacteria thrive in temperatures below 102ºF (39ºC). Their job is to acidify the milk and get it ready for the rennet. These "good" bacteria also make it more difficult for harmful bacteria to take hold in the milk. As a last resort, you can use a dash of buttermilk instead. However, store-bought buttermilk is an unpredictable source of cultures. The cheese could fail to form, or the flavor could be affected. Traditionally taken from animal stomachs, rennet is now available in vegetarian forms as well. You may use any type to form your cheese. The rennet will separate the acidified milk into curds and whey.  This is also available from cheese-making supply stores. If using dry rennet, follow the label instructions to convert drops of liquid rennet into tablet amounts. Make sure the tablets are 100% rennet. Use an infrared thermometer to measure the milk, heating until it reaches 86ºF (30ºC). Non-chipped enameled pans or stainless pans are your best options. Stay way from copper and aluminum, which leach chemicals into your cheese due to the cheese's acidity.  You may use raw milk or pasteurized milk, although cheese made from pasteurized milk may have trouble holding together. Ultra-pasteurized milk will not work. You can use milk with any fat percentage. Whole milk typically has a richer flavor than low-fat or skim milk. Let sit for two minutes. After two minutes, stir with an up and down motion to mix it into the milk. Leave the milk in a warm room away from light. The label on your starter bacteria may specify the length of this step. If it does not, or if you are using buttermilk, continue after two to four hours. The milk should still look like ordinary milk. If it thickens, you've used too much acid or left it too long. (This is easy to do, since it's difficult to predict exactly how active the bacteria will...

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Write a summary of the previous text in Vietnamese:
Mua các loại men phô-mai. Mua men rennet. Đun nóng sữa trong một chiếc nồi thép nguyên chất. Cho men vi sinh (cấy men) vào sữa. Bọc lại và để hỗn hợp nghỉ. Làm ấm sữa và cho men rennet vào. Bọc lại và để hỗn hợp nghỉ từ 4 tới 12 giờ. Tách bớt đạm whey đi. Cắt phô-mai thành từng miếng vuông nhỏ và đun nóng. Hoàn thành món phô-mai. Học thêm một vài công thức làm phô-mai khác.