For nicotine enthusiasts, 2015 will be remembered as part of a golden era. Less than 10 years after they were introduced in the United States, e-cigarettes have gone relatively unregulated by health agencies, with companies and users making their own rules in a nicotine-laced Wild West. E-cigarette companies have been advertising their products to adults and children alike, claiming to help smokers quit while simultaneously promoting lollipop-flavored liquids. But now health organizations, including the Centers for Disease Control and Prevention and even city-based public health departments are starting to fight back—not in the form of regulations, but with their own...