Engineering processes have had an even broader effect on the practice of medicine. The 20th century's string of victories over microbial diseases resulted from the discovery and creation of new drugs and vaccines, such as the polio vaccine and the whole array of antibiotics. Engineering approaches—including manufacturing techniques and systems design—played significant roles in both the development of these medications and their wide availability to the many people around the world who need them. For example, engineers are involved in designing processes for chemical synthesis of medicines and building such devices as bioreactors to "grow" vaccines. And assembly line know-how, another product of the engineering mind, is crucial to the mixing, shaping, packaging, and delivering of drugs in their myriad forms.

It may be in the operating room rather than the pharmaceutical factory, however, that engineering has had a more obvious impact. A number of systems have increased the surgeon's operating capacity, especially during the last half of the century. One of the first was the operating microscope, invented by the German company Zeiss in the early 1950s. By giving surgeons a magnified view, the operating microscope made it possible to perform all manner of intricate procedures, from delicate operations on the eye and the small bones of the inner ear to the reconnection of nerves and even the tiniest blood vessels—a skill that has enabled more effective skin grafting as well as the reattachment of severed limbs.

At about the same time as the invention of the operating microscope, a British researcher named Harold Hopkins helped perfect two devices that further revolutionized surgeons' work: the fiber-optic endoscope and the laparoscope. Both are hollow tubes containing a fiber-optic cable that allows doctors to see and work inside the body without opening it up. Endoscopes, which are flexible, can be fed into internal organs such as the stomach or intestines without an incision and are designed to look for growths and other anomalies. Laparoscopes are rigid and require a small incision, but because they are stiff, they enable the surgeon to remove or repair internal tissues by manipulating tiny blades, scissors, or other surgical tools attached to the end of the laparoscope or fed through it.

Further advances in such minimally invasive techniques began to blur the line between diagnosis and treatment. In the 1960s a radiologist named Charles Dotter erased that line altogether when he developed methods of using radiological catheters—narrow flexible tubes that can be seen with imaging devices—not just to gain views of blood vessels in and around the kidney but also to clear blocked arteries. Dotter was a tinkerer of the very best sort and was constantly inventing his own equipment, often adapting such unlikely materials as guitar strings, strips of vinyl insulation, and in one case an automobile speedometer cable to create more effective interventional tools.