They look like the real thing. The end glows as you inhale. As you exhale, you puff out a cloud of what looks like smoke. It's vapor, similar to the fog you might see at rock shows, says M. Brad Drummond, MD. He's an assistant professor of medicine at Johns Hopkins University School of Medicine.
All e-cigarettes work basically the same way. Inside, there's a battery, a heating element, and a cartridge that holds nicotine and other liquids and flavorings. Features and costs vary. Some are disposable. Others have a rechargeable battery and refillable cartridges.
Using an e-cigarette is called "vaping."The nicotine inside the cartridges is addictive. When you stop using it, you can get withdrawal symptoms including feeling irritable, depressed, restless and anxious.