Microfoam is a byprouct of heating milk with a steam wand on an espresso machine. It is created by denaturing milk proteins such as casein and whey; the protein attracts and holds gas on its surfaces, creating microfoam. Strictly speaking, microfoam is actually a very fine emulsion of denatured milk protein and air which has few or no visible bubbles. The qualitative opposite of microfoam is macrofoam, which does have visibly large bubbles. After the milk is steamed in a stainless steel container, it can be swirled in a smooth, circular motion, 5 to 10 times, until the foam on top mixes slightly with the warmed milk, to create a microfoam mixture suitable for use in espresso drinks.