A colloidal solution is a heterogeneous system that has particles ranging between 1 and 1000 nanometers in diameter, yet are still able to remain evenly distributed throughout the solution. These are also known as colloidal dispersions because the substances remain dispersed and do not settle to the bottom of the container.
In colloids, one substance is evenly dispersed in another. The substance being dispersed is referred to as being in the dispersed phase, while the substance in which it is dispersed is known as the dispersion medium.
Example :
i. Milk ( liquid in liquid - emulsion)
ii. Smoke (solid in gas - aerosol)