A colloid is a continuous medium that contains a dispersion of different particles. Colloids are microscopic particles that can be found in all-natural water. Colloids are small particles with a typical size of between 1 nm and 1 m. They can act as carriers for low-solubility radionuclides like plutonium, americium, and cesium and are made up of inorganic, organic, or microbiological material. Some actinides can hydrolyse to generate oxides or intrinsic colloids, which are pure phases. The affinity of the dispersed phase for the dispersion and the state in which the material is found in the phases that make up the colloid are the two basic criteria used to classify colloids. Lyophilic colloids are those in which the dispersed particles have an affinity for the dispersing medium, whereas lyophobic colloids resist the dispersant.