Filling up a specially adapted Mercedes, the gas-bot at the Institut Produktionstechnik und Automatisierung (IPA), a government-industry research center in Stuttgart, Germany, is intended for a time in the future when automobiles run on hydrogen. Hydrogen is an environmentally sound fuel?its main effluent is water. But it is also so explosive that robots may end up topping off people's tanks. A somewhat similar system for dispensing ordinary gasoline is currently being test-marketed by Shell in the American Midwest. From the book Robo sapiens: Evolution of a New Species, page 195.