Whipping cream is a dairy product that contains a lot of milk fat—usually around 30% or more. Cream comes from skimming off the top of fresh milk, where most of the milk fat has risen. The fat from the cream is contained in tiny droplets, like mini balloons too small to see without a microscope. When you whip cream, you're introducing millions of tiny air bubbles into the liquid. First the cream gets foamy, but as you continue whipping, you strip away the protective outer membranes on the fat balloons. This allows the fat to join together and gradually form protective bubbles around the tiny pockets of air. Like butter, it's also an emulsion. In fact, if you whip it long enough, it will turn into butter! Air suspended in liquid and held stable by fat - and is also why you need cream with a relatively high fat content (at least 30%) in order to whip cream. The less fat, the thinner the fat globules are stretched and the harder it is to make a stable emulsion.