Description:
E-cigarettes are battery operated nicotine inhalers that consist of a rechargeable lithium battery, a cartridge called a cartomizer and an LED that lights up at the end when you puff on the e-cigarette to simulate the burn of a tobacco cigarette. The cartomizer is filled with an e-liquid that typically contains the chemical propylene glycol along with nicotine, flavoring and other additives.
http://www.nicotineriver.com/blogs/news/19119035-five-fact-about-vaping