E-cigarettes release a vapor that allows users to inhale nicotine without the toxins associated with tobacco. Since they started in China a few years ago, they've become an industry worth hundreds of millions of dollars. The Centers for Disease Control report that 10% of American high school kids tried e-cigarettes last year -- twice as many as the year before. They're hip for celebrities and popular for helping smokers to quit. Big Tobacco is taking notice. Mike Esterl reports for the Wall Street Journal.