Tofu is made from soybean milk. Soy bean milk is made from mature white soybeans, which is then boiled, curdled, and pressed, in a very similar way to how cheese is made. To make the milk, the soybeans are first soaked, then ground up and warmed with water. They are then strained and become soy milk. That milk is then combined with a coagulant and simmered until the curds and whey separate, then the curds are placed into molds and pressed until the whey drains out and a block of tofu is left. The firmness of the tofu depends on how long it is pressed. If it is pressed longer, more whey is removed, creating firmer tofu.