Physicists all over the world, back in 1895, were pretty much agreed that the great work of physics had all been done. Some of them mourned publicly that no discoveries of truly major importance were likely to be made in the future. But then they did not know that a Professor Roentgen, working alone in a modest laboratory in Germany, had begun a series of experiments with a crude induction coil, a pear-shaped bulb from which the air had been removed, and a sheet of paper painted with certain metallic salts. And professor Roentgen did not know that his work was destined to reveal a force of nature—never before suspected—that would almost overnight revolutionize medicine and technology, and become an instrument for deeper probing of the structure of matter.