The FDA faces a balancing act. If the regulations are too strict, they could kill an industry that offers a hope of being safer than cigarettes and potentially helping smokers quit them. But the agency also has to be sure e-cigarettes really are safer and aren't hooking children on an addictive drug.
Members of Congress and several public health groups have raised safety concerns over e-cigarettes, questioned their marketing tactics and called on regulators to address those worries quickly.
Here's a primer on e-cigarettes and their future:
WHAT ARE E-CIGARETTES?
E-cigarettes are plastic or metal tubes, usually the size of a cigarette, that heat a liquid nicotine solution instead of burning tobacco. That creates vapor that users inhale.
Smokers like e-cigarettes because the nicotine-infused vapor looks like smoke but doesn't contain the thousands of chemicals, tar or odor of regular cigarettes. Some smokers use e-cigarettes as a way to quit smoking tobacco, or to cut down.
The industry started on the Internet and at shopping-mall kiosks and has rocketed from thousands of users in 2006 to several million worldwide who can choose from more than 200 brands. Sales are estimated to have reached nearly $2 billion in 2013.
Tobacco company executives have noted that they are eating into traditional cigarette sales. Their companies have jumped into the business.
There's not much scientific evidence showing e-cigarettes help smokers quit or smoke less, and it's unclear how safe they are.
WHAT IS THE FDA LIKELY TO DO?
The FDA is likely to propose restrictions that mirror those on regular cigarettes.
The most likely of the FDA's actions will be to ban the sale of e-cigarettes to people under 18. Many companies already restrict sales to minors, and more than two dozen states already have banned selling them to young people.
Federal regulators also are expected to set product standards and require companies to disclose their ingredients and place health warning labels on packages and other advertising.
Where the real questions remain is how the agency will treat the thousands of flavors available for e-cigarettes. While some companies are limiting offerings to tobacco and menthol flavors, others are selling candy-like flavors like cherry and strawberry.
Flavors other than menthol are banned for regular cigarettes over concerns that flavored tobacco targets children.