Milk is a combination of fats, proteins, and water. When raw milk is left to stand for any length of time, the fat molecules typically float to the top. Homogenization is the process of breaking down the fat globules in milk so that they stay integrated rather than separating as cream. Homogenization is a purely physical process, nothing is added to the milk. Some scientists argue that milk is more digestible when homogenized and others argue that the milk fat globules are too rapidly absorbed when homogenized.