Mayonnaise is a culinary triumph of chemistry called a stable emulsion. The story goes that it was invented to celebrate the French capture of Mahón (on the island of Menorca) in 1756. The chef of the Duke de Richelieu, unable to find cream for a victory sauce, substituted olive oil and egg yolks. Chemically, mayonnaise is difficult to make because oil and vinegar naturally repel each other. Egg yolks contain lecithin, an emulsifier that has one end attracted to water and the other to oil. This holds the tiny droplets of oil in suspension within the vinegar, creating the creamy, thick texture. If the oil is added too quickly, the emulsion 'breaks,' and the sauce turns into a greasy liquid. Today, it is the most popular condiment in the United States, outselling even ketchup.