Beating swords into plowshares—that's how advocates of nuclear technology have long characterized efforts to develop peaceful applications of the atom's energy. In an ongoing controversy, opponents point to the destructive potential and say that, despite the benefits, this is almost always a tool too dangerous to use. Beyond the controversy, however, lies the story of scientific and engineering breakthroughs that unfolded over a remarkably short period of time—with unprecedented effects on the world, for both good and ill.