In 1963, a patent was filed for a “smokeless non-tobacco cigarette,” but the invention did not take off. Forty years later, in 2003, Hon Lik, a Chinese pharmacist whose father had died of smoking-induced lung cancer, patented a similar device—this time, reimagined with nicotine. Fast-forward ten more years, to 2013, and electronic cigarettes—or e-cigs, as they’re often called— had mushroomed into a billion-dollar industry. Last year also marked the moment when a leading manufacturer of the device, NJOY, aired an ad during the Super Bowl, to the tune of Avicii’s popular “Hey Brother.” The ad reaches a crescendo with this line: “Friends don’t let friends smoke. Give them the only electronic cigarette worth switching to.”

E-cigarettes are not cigarettes. As the name suggests, they simulate smoking and, via an inner heating element, deliver nicotine through the vapor of liquid nicotine instead of the combustion of tobacco leaves. That’s why e-cigarettes are often promoted as a safer alternative to smoking. But the public-health debate is in full bloom. Trace amounts of toxic substances have been detected in e-cigarettes, and their usage among youth doubled in 2012. Yet many cite the devices as remedies that can stop their decades-long tobacco-smoking habits.

In New York City, in the evenings, “vapers,” as they’re called, gather around a long table in the back of the Henley Vaporium, on the border of Nolita and SoHo, to discuss liquid-nicotine flavors (“Have you tried the new custard?”) and to “rebuild” their e-cigs. The first time I passed the Vaporium’s cloudy windows, I peered inside to see beyond the smoke. “Welcome,” a young, bearded man offered, as I sat down next to him at the table in the back. The video above is a glimpse into that world.