The continuous-flow process is the most commonly used method in the manufacture of margarine. If milk is used as the liquid base, it is joined with salt and an emulsifying agent in a chamber. The emulsifying agent ensures that the emulsification process—chemically defined as a suspension of small globules of one liquid in a second liquid—takes place. An emulsifier works by decreasing the surface tension between the oil globules and the liquid mixture, thereby helping them form chemical bonds more easily. The result is a substance that is neither wholly liquid nor wholly solid but rather a combination of the two called semi-solid. Lecithin, a natural fat derived from egg yolk, soybean, or corn, is one typical emulsification agent used in margarine manufacturing.