When on dissolution a large number of atoms or smaller molecules of a substance (with diameters less than `1` nm) aggregate together to form species having size in the colloidal range, the species thus formed are called multimolecular as colloids. For example, sulphur sol consists of colloidal particles, which are aggregates of `S_8` molecules. A metal sol consists of particles of various sizes, which are clusters of several metal atoms. The atoms or molecules in each aggregate are held by Vander Waal's forces.

In this type of colloids, colloidal particles are themselves large molecules having colloidal dimensions i.e., (`1-100` nm). They are polymers having very high molecular mass. They include natural polymers such as starch, proteins, cellulose and synthetic polymers such as polythene, polyester and nylon etc.

This type of colloids includes substances, which behave as true solutions at low concentrations but become colloidal in nature at high concentrations due to the formation of aggregated particles called micelles. Soaps and detergents are examples of associated colloids. In aqueous solution sodium stearate (a kind of soap) ionises as

`C_(17)H_(35)COONa -> Na^+ + C_17H_35COO^(-)`