With similar reasoning, thermodynamics tells us that emulsions and foams should not exist because they require huge quantities of energy bound up in interfaces. However, this author, despite thermodynamics, has a glass of milk next to him. It could eventually (e.g., in a few months) separate into a layer of fat over a layer of water if it remains undisturbed, but for the moment it is stable. As discussed in Chapter 6, before an emulsion or foam is destroyed by physical laws (thermodynamics), it can remain stable for a period of time (kinetics).