Whether you call them "hookah pens" or "e-hookahs," or "vape pipes," they are all now illegal to anyone under the age of 18 in the United States.
Citing potential health risks, the U.S. government announced in May that electronic cigarettes will be regulated just like other tobacco products.
That's important because e-cigarettes have become increasingly popular with young people, many of whom are drawn to candy- and alcohol-themed flavors, such as strawberry mimosa, watermelon mojito and chocolate cherry.
But the e-cigarettes, vaporizers and hookah pens all use liquid that contains nicotine, in addition to the flavorings. (They also contain propylene glycol, glycerin and other ingredients.) The liquid is heated into an aerosol that the user inhales.
Recent data shows that the share of secondary school students in the U.S. who are "vaping" (an estimated 16 percent) exceeds the share that smokes traditional cigarettes (9 percent). Scientists still are debating whether e-cigarettes are safe, but many people believe they are, and that belief is behind the trend.
Worldwide, since 2005 the e-cigarette industry has grown from one manufacturer in China to an estimated $3 billion global business with 466 brands, according to the World Health Organization, which has raised concerns about the tobacco industry's role in this market.