(FORTUNE Magazine) – They gave their huge machines names like Stellarator Magnetic Confinement System and saw themselves as 20th-century Prometheuses -- stealing nuclear fire from the heavens and taming it on earth. They had the arrogance of demigods. ''For a billionth of a second on this earth,'' one of them said once, ''we have created fractions of heaven.'' Over four decades, fusion physicists tried to light man-made suns inside their monstrous devices at a cost to taxpayers of at least $5 billion. Then, two guys with a glass jar punctured the pride of the fusion clique. B. Stanley Pons, a University of Utah chemist, and Martin Fleischmann, an electrochemist at Britain's University of Southampton, claimed they had achieved fusion in a tabletop experiment. In an age of government-funded technology projects, Pons and Fleischmann spent $100,000 of their own money. They applied an electric current to palladium rods immersed in a flask filled with heavy water (which contains deuterium, an isotope of hydrogen). Fusion -- the merger of these hydrogen atoms -- appears to take place in the palladium rods, releasing heat and telltale neutrons. Fusion promises a cleaner, more efficient, and much more abundant source of energy than any in hand. One cubic foot of sea water contains enough deuterium to yield 250,000 BTUs of energy, equal to ten tons of coal. No fewer than 200 corporations, including GM, GE, and Boeing, have besieged the University of Utah for more information. Howard E. Simmons, Du Pont's vice president for central R&D, says, ''This could have a great impact on all our futures.'' Skeptical scientists grudgingly concede some fusion is taking place, but they want more confirmation. Since even the discoverers aren't completely sure how the process works, translating the miracle in a bottle to commercial products looks a long way off, if ever.