You'll never worry about misplacing your lighter or your matches if you're smoking an e-cigarette -- there's nothing to light. Instead, e-cigarettes run on a lithium battery; each also contains a vaporization chamber and a cartridge filled with liquid. When you puff on your e-cig as you would a regular cigarette, the battery powers the device to heat the liquid and vaporize it. Some e-cigarettes have a cigarette-like LED tip that glows red (or another color, depending on the product you're using), but not all of these smokeless gadgets resemble regular cigarettes. Because they don't burn tobacco, there's no smoke, no carbon monoxide and no odor; what you inhale is vapor [source: FDA].