The definition of colloid chemistry is the science of the composition, properties, structure, and reactions of matter, especially of molecular and atomic systems. It is the study of colloids. A colloid is a substance microscopically dispersed evenly throughout another one and they play an important part in industry. Colloid chemistry is a sector of chemistry. The importance of research of colloid chemistry in industry helps understand the make up of modern products including medicines. Many foods are colloidal in nature including milk.