It's a dream that's been pursued for years by governments, energy companies and automakers so far without success: Mass-producing affordable hydrogen-powered cars that spew just clean water from their tailpipes.

So Shanghai's Horizon Fuel Cell Technologies decided to start small. Really small.

This month, it will begin sales of a tiny hydrogen fuel-cell car, complete with its own miniature solar-powered refueling station. The toy is a step toward introducing the technology to the public and making it commercially viable.