When a recipe specifies using only two or three ingredients, such as egg whites, sugar, and an acid, achieving perfection can be a challenge, as is the case with meringue. So it is helpful to understand the chemistry of egg foams. See eggs. Egg whites are composed of proteins and water. When beaten and combined with air, the albumen, or thick white of the egg, separates into gaseous foam, a stable mass of tiny bubbles coated with a thin layer of water. When air and acid are incorporated into the whites, or when the mixture is exposed to heat with the help of steam, the bonds of the whites unfold, denaturing the proteins and making it possible for them to join and solidify. As meringue cooks, another protein, called the ovalbumin, goes to work and changes the fluid foam into one that is solid, thus preventing collapse of the structure.