A colloid is a mixture where tiny particles are dispersed throughout a substance but do not settle out. These particles are larger than those in a solution but smaller than those in a suspension, typically ranging from 1 nanometer to 1 micrometer in size. Common examples of colloids include milk, fog, and paint. Colloids can be classified into different types based on the phases involved, such as aerosols (solid or liquid particles in a gas) and emulsions (liquid droplets in another liquid). The stability of colloids is often maintained by the interactions between the dispersed particles and the medium in which they are suspended.