This article was taken from the March 2016 issue of Wired magazine. Be the first to read Wired's articles in print before they're posted online, and get your hands on loads of additional content by subscribing online.WIRED deconstructs e-cigarette juice to find out what you're breathing in every time you vape.WATER Many "vape juice" flavours include good old H20. A reservoir for liquid and a heating element are the basic components of e-cigarette devices. A wicking material such as cotton pulls the liquid towards a metal coil, where heat turns it into droplets that are tiny enough to inhale.VEGETABLE GLYCERINYou've probably consumed this sugar alcohol in food as a low-glycemic sweetener, a preservative, or a texture enhancer that boosts thickness. (It's also an ingredient in moisturisers.) PROPYLENE GLYCOLA tasteless, odourless, colourless alcohol used in antifreeze. Although it's considered safe for topical use and consumption, it's also an active ingredient in many fog-machine juices, which can act as allergens and cause eye and airway irritation. It can also cause headaches, dizziness and drowsiness.Don't missE-cigarette licensed as quit-smoking medication E-cigarette licensed as quit-smoking medicationFLAVOURINGThe names of e-cig flavours are amazing: Unicorn Milk; Krispy Krack Doughnut; Pony on Acid! Manufacturers usually don't reveal ingredients on the grounds that they're "tradesecrets". Many assert that their flavourings are food-grade and safe.NICOTINE In its inhaled particulate form, nicotine itself is pretty safe -- unless you're a child or a gestating foetus in a vaper. But in liquid form, even tiny amounts that are ingested or make contact with skin can induce vomiting, seizures and even death. Wear gloves when you refill.