in water) and a vaporization chamber, which produce an aerosol that simulates the smoke of a cigarette ( fig. 1 ).Nicotine and other additives like flavorings and glycerol (purified vegetable glycerine) may be added in various concentrations to the liquid. No combustion is involved in the process and the 'smoke' produced is an aerosol of liquid particles, a 'mist' [1] .Advertised as a valid way to quit smoking real cigarettes, the e-cigarette has been the subject of much controversy but little experimental study. This review provides a brief overview of the current evidence on the ecigarette. Aerosol GenerationBesides water, the main ingredient of the e-liquid is usually propylene glycol (PG) in water. A mechanical sensor detects when the user inhales and it then triggers the microchip controlling the heater which raises the temperature in the vaporization chamber.As specified by the manufacturers, the temperatures in the vaporization chamber range from 40 to 65 ° C [1] . Recently, however, variable voltage devices gained popularity as they can increase the temperature of operation and the heater surface area in order to tune the vapor to the user's satisfaction. No reliable data could be found on the range of temperatures in these recent devices. The same uncertainty exists about the operating temperature in Key WordsElectronic cigarettes · Propylene glycol · Nicotine AbstractMarketed since 2004 as an alternative to nicotine delivery and advertised as a valid means to smoking cessation, the electronic (e)-cigarette has been the subject of much controversy but very little experimental study. This review provides a brief summary of the current knowledge of this product. Propylene glycol and glycerol, the main ingredients of the fluid that is vaporized, have proved to be harmless in the fog machines of the entertainment industry. However, in the case of the e-cigarette fluid, the composition is not properly labeled: additives like nicotine and flavors vary between and within brands and contamination with various chemicals has been detected. The short-term toxicity seems low, but the long-term toxicity is unknown. The usefulness of the e-cigarette in smoking cessation has still to be clinically established.