A car that emits only water vapor: It sounds almost too good to be true. Yet, such a vehicle already exists. It uses a hydrogen fuel cell to generate electricity and drive its motor. Several problems still need to be addressed however. The first problem is to produce "clean" hydrogen from renewable electricity sources, rather than from fossil fuels, in order to effectively reduce pollution. The second is to develop leak-proof, corrosion-resistant tanks for storing hydrogen. Manufacturers have taken up the challenge of developing dependable tanks that are affordable and cost-effective. Several models, while still expensive, are close to being commercialized.