As smoking becomes redundant and stigmatized due to the obvious, in your face, health risks; many alternatives have emerged creating the market of vapor products. I've tried them all, one after another, none did the trick of smoking a cigarette.
Then came the JUUL... Its small, discrete, tasty, and doesn't have to be refilled. It uses replaceable vapor pods that each contain the equivalent of nicotine as a pack of cigarettes. The real difference is that JUUL uses salt juice which hits you instantly, opposed to about 30 minutes with normal e-juice.
Are they ok for your lungs?
Yes, it produces a very small amount of vapor compared to the fog-machine vapes out there. Vapor in general is much healthier than smoking.