History of the Microscope

It seems like the sort of discovery that a child would make during play: looking through a piece of glass or crystal that's thicker at its center causes objects to look larger. Though magnifying glasses were known and used for many years, it wasn't until the early 1600s that the magnifying power of glass was enhanced and given scientific application via the microscope, an instrument that forever transformed the way we see our world.

Who invented the microscope? The first microscopes were optical microscopes, aka light microscopes, so called because they use light that's visible to the human eye. They come in two forms: simple microscopes, i.e. single lens, and compound microscopes, i.e. multiple lenses. Like the evolution of the eye, the invention of the microscope was an ongoing process that likely occurred independently in more than one location. Primacy is generally given to the Dutch spectacle maker Hans Janssen and his son Zacharias, and dated to the early 1590s. As described by the Dutch diplomat William Boreel in a letter written some six decades later, the Janssen's invention was a compound microscope nearly two and a half feet long, with a two-inch diameter tube, and a convex lens at one end and concave lens at the other. Its magnifying power was reportedly between 3x and 9x.

Who invented the microscope?
The first microscopes were optical microscopes, aka light microscopes, so called because they use light that's visible to the human eye. They come in two forms: simple microscopes, i.e. single lens, and compound microscopes, i.e. multiple lenses.

Like the evolution of the eye, the invention of the microscope was an ongoing process that likely occurred independently in more than one location. Primacy is generally given to the Dutch spectacle maker Hans Janssen and his son Zacharias, and dated to the early 1590s. As described by the Dutch diplomat William Boreel in a letter written some six decades later, the Janssen's invention was a compound microscope nearly two and a half feet long, with a two-inch diameter tube, and a convex lens at one end and concave lens at the other. Its magnifying power was reportedly between 3x and 9x.

Galileo's compound microscope
In his 1623 work The Assayer, Galileo refers to "a telescope modified to see objects very close." In 1609, Galileo had used a telescope at short range to view insects, and his fascination with the results is what led to the invention of his own compound microscope. Galileo's word for it was occhialino, or little eye. Giovanni Faber, a fellow member of the Lincean Academy, coined the term microscope in 1625. Illustrations of insects seen through one of Galileo's microscopes were printed that same year.

The first electron microscope
Despite centuries of improvements in microscope design, magnification and resolution were ultimately limited by the wave nature of light. This challenge was overcome in the early 1930s by Ernst Ruska and Max Knoll, who constructed the first electron microscope. Electron microscopes far exceed the resolution capabilities of optical microscopes, because the specimen is illuminated not by photons, but by a beam of electrons, which have a much shorter wavelength than visible light- about 12.3 picometers vs. about 400nm, a ratio of approximately 1:32,500. In 1986, Ruska was named co-winner of the Nobel Prize in Physics "for his fundamental work in electron optics, and for the design of the first electron microscope."

Stereo microscopes, digital microscopes...
While electron microscopes are principally used for advanced scientific research, today's amateur microscopist has access to an extraordinary variety of different microscope designs with magnifying power that Galileo could only have imagined. From stereo microscopes that offer three-dimensional images to stamp collectors and entomologists, to digital microscopes that completely eliminate the need for an eyepiece, there's no limit to which, in Galileo's words, "the greatness of nature can be infinitely contemplated."