Electronic cigarettes or ENDS (electronic nicotine delivery systems) are devices whose function is to vaporize and deliver to the lungs of the user a chemical mixture typically composed of nicotine, propylene glycol and other chemicals, although some products claim to contain no nicotine. A number of ENDS are offered in flavours that can be particularly attractive to adolescents. Electronic cigarettes (e-cigs) are the most common prototype of ENDS.