(I)  The colloidal particles in multi-molecular colloids are an assemblage of atoms or tiny molecules having a diameter of less than 1 nm. The molecules in the aggregate are held together by Van der Waal’s forces of attraction. Gold sol and sulfur sol are two examples of such colloids.

(II) Large molecules with colloidal dimensions in the shape of colloidal particles are macromolecular colloids. The molecular mass of these particles is very high. When these particles are dissolved in a liquid, they produce sol. For instance, starch, nylon, cellulose, and so on.

At low concentrations, certain substances tend to behave like normal electrolytes. However, at higher concentrations, due to the formation of aggregated particles these substances behave like colloidal solutions. Such colloids are called aggregated colloids