A typical electronic cigarette has the following components:
The mouthpiece - the replaceable cartridge is placed here. The user sucks or inhales from the mouthpiece.
The atomizer - a heating element which vaporizes the liquid solution. The vapors are inhaled. In most devices, the atomizer needs to be replaced every three to six months.
The battery - this is usually a rechargeable lithium-ion rechargeable battery. The battery is the power-source for the heating element. There is also some electronic circuitry in the device, such as the airflow sensor, a timed cutoff switch to prevent overheating, and a colored LED (light emitting diode) to indicate the device has been activated.
Electronic cigarettes are becoming increasingly popular, especially in Western Europe. It is estimated that many tens of millions of people worldwide are regular users.