Almost any liquid works – water, beer, urine. Yes, that's right. Just insert any liquid into the base with a pipette. The batteries come in a range of sizes and contain no dangerous chemicals, such as mercury, lead or cadmium. Inside, a mixture of carbon and magnesium reacts with the liquid to produce power. However, they can only be refilled a finite number of times.

Apparently they can also be connected in a series to create larger power cells, which can power larger items, such as lamps. But think of the potential – could we someday power our refrigerators, or even cars, with water?

They're currently only sold in Japan, but they could hit the West by early 2008.