Colloids are mixtures where tiny particles, typically ranging from 1 nanometer to 1 micrometer in size, are dispersed throughout another substance, usually a liquid or gas. These particles are small enough to remain suspended and do not settle out over time, unlike larger particles in suspensions. Common examples of colloids include milk, fog, and paint. The properties of colloids can vary widely depending on the nature of the dispersed particles and the medium. They often exhibit unique behaviors, such as the Tyndall effect, where light is scattered by the particles, making the path of the light visible. Colloids play important roles in various fields, including food science, medicine, and materials engineering.