Will e-cigarettes make the traditional cigarette obsolete? Vaping is catching on among smokers switching from cigarettes, but it is also attracting a new demographic: young people who’d never smoked before. Tony Dokoupil reports on the possible benefits and unknown effects of transitioning tobacco products to a smoke-free market, and talks with health officials; representatives of tobacco companies and e-cig firms like Juul and Mountain Oaks Vapors; and a San Francisco official who led a fight against flavored smoking products that are believed to attract young people to nicotine use.