An electronic cigarette, or e-cigarette, is an electrical device that simulates the act of tobacco smoking by producing an inhaled vapor bearing the physical sensation, appearance, and often the flavor (with or without nicotine content) of inhaled tobacco smoke, without its odor or, ostensibly, its health risks. The device uses heat (or in some cases, ultrasonics) to vaporize a propylene glycol- or glycerin-based liquid solution into an aerosol mist, similar to the way a nebulizer or humidifier vaporizes solutions for inhalation.