Cigarette smoke is a result of combustion. During the combustion process, particulate matters are formed when products of combustion and high-temperature pyrolysis reach high enough concentration to nucleate via condensation, or when they interact with each other to form liquid particulate matter (droplets) and solid particulate matter (soot). Although smoke is an aerosol, this mix of gases, liquid droplets, and solid particles formed during combustion is what makes smoke different from other aerosols.