Smoking is cool again. Who would have thought? Just when many thought smoking was on the decline, with stomach-churning advertisements of charred lungs on public television and the preeminence of smoke-free environments, an alternative form of nicotine delivery is gaining popularity: high-tech e-cigarettes. One of the most popular of these is the JUUL, which accounts for 32 percent of the U.S. e-cigarette market share. The JUUL is about one-fifth the size of an iPhone and uses patented nicotine juice cartridges, called JUULpods.