A homogenizer works by breaking down the fat globules in the milk and forcing them to regroup, then breaking up the layers that form so the globules inside of the solution remain at the desired sizes, explains How Stuff Works. This process has been gradually improved since French inventor Auguste Gaulin's first homogenizing process was patented in 1899.
Homogenization is the process of reducing the fat globules in milk to such a small size that they float suspended evenly throughout the entire milk solution. Raw milk is an emulsion, a mixture of milk-fat globules, solids and water. Without the process of homogenization, milk forms two different layers. The bottom layer consists entirely of skim milk. The second layer is made up of fat globules and forms a creamy surface on top of the milk.
Homogenizers work in two stages. In the first stage, these devices press milk through extremely small tubes or pores. These pores continue to shrink as the milk flows through them, increasing the pressure inside the homogenizer. This forces the fat globules in the milk to break apart. Eventually, they form new clumps of fat mass. Afterward, a homogenizer breaks up the clumps that have formed and reduce the fat globules to a manageable size.