Colloids are particles immersed in fluid that are so small that Brownian Motion keeps them from settling out. Dust particles are a good example of colloids in nature. To study colloids in a controlled way, one can now buy uniform sized spherical polystyrene or silica spheres in sizes ranging from a few tenths to a few tens of mircons. The interacts that occur between the colloids and other particles in the liquid result in their suspension. A good model of this can be seen on the 'Links' page under 'Brownian Motion - Visual Demonstration'. Colloids in Nature Colloidal systems are abundent in nature, occurring in clouds, blood, milk and in many other instances. Colloids in the Lab