# Why don't particles of a colloid settle?

Why don't particles of a colloid settle but those of a suspension do? - Is it because they are really small and so remain in constant motion which overcomes the force of gravity and prevents them from settling? - Is it because they are charged and so they repel each other and stay suspended in the solution as they try to go away from each other?

Particles in colloid absorb either positive or negative ion preferentially from solution depending on there surface. This develops a potential on colloid surface called Zeta potential. Due to this potential colloid particles repel each other and can't coagulate.