No less enchanting was a host of developments in the recording of images, including color photography, holography and other three-dimensional imaging, and digital photography; the invention and rapid dissemination of moving pictures and television, which quickly came to dominate Western culture; and the proliferation of cameras, camcorders, videotapes, CDs, and DVDs, which have transformed our ways of looking at the world. Imaging even came to play a vital role in such endeavors as microelectronics, where electron beams and other devices etch hundreds of millions of transistors into the surface of computer memory chips and microprocessors.

The story behind these new sorts of vision and imaging encompasses a wide range of fields, from astronomy to medicine, each with its own century-spanning plot line. Narrative threads intertwine along the way, with discoveries in one field contributing decades later to applications in another. The one common theme is how we turned new knowledge into tools that have improved our lives by changing how we see.

The first dawning rays of this new age of seeing appeared—quite literally—just before the beginning of the 20th century. In 1895 a German physicist named Wilhelm Konrad Roentgen accidentally discovered a form of radiation that could penetrate opaque objects and cast ghostly images on a photographic plate. Roentgen called his discovery X-radiation (the X was for "unknown"), and to prove its existence he took a picture of his wife's hand by exposing it to a beam of its rays. The result showed the bones of her hand and a ring on her finger as dark shadows on the photographic plate. It was the first x-ray image ever deliberately recorded.

The rays were soon identified as a form of electromagnetic radiation with wavelengths very much shorter than those of visible light. The shortness, or high frequency, of these wavelengths accounted for their penetrating power; their ability to delineate internal structure came from the fact that denser materials, such as bone, absorbed more of the rays. An American named William Coolidge soon put all this to practical effect with his 1913 invention of a vacuum tube that conveniently—and relatively safely—generated X rays. Medical doctors quickly seized on this wonderful new tool that enabled them to see, for example, how a bone was broken, or where a bullet might be lodged, or whether a lung harbored potentially lethal growths. A new field of diagnostic—and later therapeutic—medicine, radiology, was born. X rays also found their way out of the doctor's office and into the industrial world, where they were used to check for hidden cracks or other flaws in complex machinery and in structures such as bridges.