Perhaps one of the biggest ironies in biology is that microbes, which are the oldest self-replicating organisms on Earth, were among the last to be discovered and have largely been ignored. The history of their discovery is, like many in science, based on the invention of new technologies. In this case, it was a microscope created by a man named Anton van Leeuwenhoek. But before the Dutchman could make his serendipitous yet groundbreaking discovery in the late 17th century, lens-making technology had to turn several corners and see some other significant findings first.
In the 14th century, crude lenses were being fabricated in Europe for correcting vision. Toward the end of the 16th century, the Dutch began to use Venetian glass, the clearest and the highest quality glass available, to fashion relatively high-quality lenses.
Early in the 17th century, two Dutch lens-makers fashioned a telescope by pairing a concave and a convex lens in a tube. Although the instrument was not much more than a crude spyglass, having a magnification of about seven- or eightfold, it was a huge breakthrough in technology at the time.
In 1609, Galileo Galilei, using a telescope made in Italy from a Dutch lens-maker’s design, observed that the moons of Jupiter orbited that planet rather than the Earth. Although Galileo’s instrument had a magnification of only about twentyfold, it was sufficient to allow him to zoom in on what we already could see with our naked eyes: planets, stars and the moon. His observations threatened the prevailing Ptolemaic, or geocentric, understanding of the solar system and changed the way we think about our planet, ourselves and our special relationship to the universe.
Although stories of Galileo and his telescope abound, a somewhat lesser-known fact is that he also developed a microscope around 1619. It was simply an inadvertent outgrowth of the invention of the telescope, since it had been known for several years that by inverting a telescope with two lenses, one could magnify objects nearby. So, the optical design of the telescope was inverted and put into a new housing.
