"They are electronic, alternative smoking devices that simulate the sensation of smoking. They do not expose the user, or others close by, to harmful levels of cancer-causing agents and other dangerous chemicals normally associated with traditional tobacco products."

-- Craig Youngblood, president of InLife, an e-cigarette company.

"They are nicotine delivery devices intended to be used like a cigarette. What happens to someone who stops inhaling the tars of cigarettes and inhales only nicotine? We don't know. There is at least the potential for harm."

-- Norman Edelman, MD, chief medical officer, American Lung Association

"We are concerned about the potential for addiction and abuse of these products. We don't want the public to perceive them as a safer alternative to cigarettes."

-- Rita Chapelle, FDA spokeswoman.

E-cigarettes don't make real smoke, yet they've ignited a firestorm of controversy.

You may have already seen e-cigarettes -- electronic cigarettes -- for sale on the Internet or at one of at least 62 kiosks at malls across the U.S.

E-cigarettes are safer than cigarettes, their makers say or imply. But until e-cigarettes are proven safe, the FDA is refusing to let them into the country and may soon ban their sale, as major U.S. medical associations have asked.

"We have an open investigation into this issue," FDA spokeswoman Rita Chappelle tells WebMD. "What is happening right now is FDA has reviewed several e-cigarettes, e-cigars, and e-pipes, and have refused entry of these products into the country. We acted because these products appear to require FDA approval for marketing, and have not been reviewed by the agency."

An informal FDA review of some of these products "indicated that these products are not currently approved," Chappelle says.

If the FDA bans e-cigarettes, an action many observers believe imminent, it won't be the first North American agency to do so. Last month, Canada's health agency banned the importation or sale of e-cigarette products.

What's all the fuss about? At the heart of the issue is a debate over what the e-cigarette really is.