Just how cold is "cold?" Is "cold" a frosty beverage? A Minnesota February? A winter in the Antarctic? Maybe your idea of "cold" is liquid nitrogen, at (-195.8 degrees Celsius), chilly enough to freeze a rubber ball till it shatters. Maybe you think liquid helium (-270 Celsius) is really cold, and anything warmer is for wimps.

But beyond any of those things, there's something that's still colder. Absolute zero, (-273.15 degrees Celsius), the temperature at which all molecules stop moving entirely, is really, really, cold. Ultimately cold. So cold that, while scientists have been able to reach temperatures within 20 billionths of a degree above absolute zero, they have never been able to get there -- and many think they never will.

It's not for lack of trying, though. Over the years, many scientists and engineers have explored what temperature really means, and have worked on ways to alter things' temperatures. Their research has resulted in more efficient engines, air conditioning, new materials, and even a new form of matter, the Bose-Einstein Condensate.

Researchers made the smallest piece of ice possible - a hexagonal shape built out of just six molecules of water. A normal drop of water contains about 100,000,000,000,000,000,000 water molecules. The research may help the scientists examine how water molecules bond together, information of great interest to biologists, chemists, and pharmaceutical researchers.