Repeated experimentation and careful measurement-so vital to the scientific method-were greatly aided by the development of new technology. Two of the technological innovations of the Renaissance the microscope and the telescope-expanded human sight in amazing ways. One allowed scientists to look inward at the minute structures of the human body. The other opened the door to the universe beyond. Engravers, workers in fine detail, are thought to have been the first to capture water in glass globes and gaze through it as a magnification aid. Lenses appeared in the late 1200s. It is not surprising therefore that three spectacle-makers, Zacharias Janssen, his father Hans, and Hans Lippershey, have been credited with developing an early microscope with simple lenses in the final decade of the 1500s.
Less than 100 years later, in the 1670s, Anton van Leeuwenhoek had devised a microscope that allowed him to see bacteria of only 2 to 3 micrometers in diameter. Galileo, in 1609, was the first to use the compound lenses of a telescope to view the skies. The telescopes that he built were larger and more powerful than any that had been built before. What he observed with his telescope confirmed Galileo’s belief in the heliocentric views of Copernicus. Both these inventions, developed within twenty years of each other, were to open the eyes of science for centuries to come.