Colloids are mixtures where one substance of microscopically dispersed insoluble particles is suspended throughout another substance. Types of colloids include: - Sol: Solid in liquid (e.g., paint) - Emulsion: Liquid in liquid (e.g., milk, mayonnaise) - Foam: Gas in liquid (e.g., whipped cream) or Gas in solid (e.g., styrofoam) - Aerosol: Liquid in gas (e.g., fog, hairspray) or Solid in gas (e.g., smoke) - Gel: Liquid in solid (e.g., jelly)