New York - On the edge of the SoHo neighborhood downtown, The Henley Vaporium is an intimate hipster hangout with overstuffed chairs, exposed brick, friendly counter help - but no booze.

Instead, the proprietors are peddling e-cigarettes, along with bottles of liquid nicotine ready to be plucked from behind a wooden bar and turned into flavorful vapor for a lung hit with a kick that is intended to simulate traditional smoking. A hint of banana nut bread e-juice lingered in the air one recent afternoon as patrons gathered around a low table to chat and vape, or sidled up to the inviting bar for help from a knowledgeable "vapologist."

Places like The Henley are a rarity, even in New York. But "vaping," itself, has had astonishing growth - in just eight years or so, the number of enthusiasts around the world has grown from a few thousand to millions. Believed by some to be the invention of a Chinese pharmacist, vaping now has its own YouTube gurus, trade associations, lobbyists, online forums and vapefests for meet-ups centered on what enthusiasts consider a safer alternative to the "analog," their name for tobacco cigarettes.

The Food and Drug Administration plans to regulate e-cigarettes but has not yet issued proposed rules. The agency simply states on its website that "e-cigarettes have not been fully studied so consumers currently don't know the potential risks of e-cigarettes," including how much nicotine or other chemicals are inhaled, or if e-cigs "may lead young people to try ... conventional cigarettes."

Whether vaping helps regular smokers quit or leads non-smokers to nicotine addiction isn't known. Vaping may be safer - there are differing opinions - but it isn't necessarily cheap.

Will Hopkins, a 21-year-old dog walker in black leather jacket and skull ring, visits Henley four or five times a week. He smoked a pack of full-strength Marlboros a day for eight years, until he took up vaping. The same goes for his buddy, 20-year-old photographer Will Gallagher, who has been vaping for two years and is fond of his brass mod, a cylindrical device that's larger than a cigarette and decorated with a tiger and Chinese lettering.

"I think both of us have poured in probably a little over a thousand" dollars, Gallagher said of their equipment. "I like the exclusivity of vaping. I like to keep changing up my stuff."

E-cigarettes are usually made of metal parts combined with plastic or glass and come in a variety of shapes and sizes. They heat the liquid nicotine solution, creating vapor that quickly dissipates when exhaled. The vapor looks like tobacco smoke and can feel like tobacco smoke when taken into the lungs at varying strengths, from no nicotine up to 24 milligrams or more.

There are more than 250 brands and devices that can cost mere dollars for a case of "cigalikes," which resemble the real thing, to a gold-and-diamond unit the size of a fountain pen that was reportedly made for a Russian oil tycoon and cost about $900,000.

Whether vaping is cheaper than a cigarette habit is up to how much is spent on equipment and liquids and how often one vapes. A 15-milliliter bottle of liquid at Henley can go for $12 and may be roughly the equivalent of four packs of cigarettes. Rechargeable devices require batteries and a starter kit for reuse that comes with a device can run around $66.