Don't go into the Molecule Cafe thinking you can sit down with a coffee and a croissant. In fact, don't even think about ordering anything besides water -- because that's the only thing on Molecule Cafe's menu.

The restaurant sells only filtered tap water, which, according to the restaurant owners, is free of fluoride, chlorine and other metals. To ensure this, the cafe employs an 8-foot-tall machine (that cost $25,000) to treat the water via reverse osmosis, ultraviolet rays and ozone treatments. Along with bottles of water, which is also sold in gallons for use at home, the cafe offers vitamin supplements customers can add to their water to improve their aspects of their health -- for example, get stronger bones or improve their "night vision."

The impetus behind the Molecule Cafe? As Adam Ruhf, the co-owner, says, "It’s about treating water a little more consciously, mindfully and respectfully. This is like a water store 2.0.”