Microscope: the first window on the tiny world

A fly’s wing, a thin onion skin or a drop of water: to the eye, there is nothing special in them. Under a microscope, the same things become a whole world, with tiny cells, veins and small living creatures in motion. This world always existed. But the window to see it opened in the spectacle-makers’ shops of the Netherlands in the late sixteenth century.

A city of lenses

In Part 43 of this series, we saw that reading glasses were made in Italy in the late thirteenth century. After that, grinding glass into lenses became a proper craft. In the next part, we will see that a spectacle maker in the Dutch city of Middelburg made the first application for the telescope. The story of the microscope is also linked to the same city.

Alan Chodos, former editor of APS News, the journal of the American Physical Society, writes that the compound microscope is usually credited to Zacharias Janssen, son of Hans Janssen, a spectacle maker of Middelburg. Zacharias was still a teenager in the 1590s. Historians therefore believe his father must also have played an important role.

The date of the invention is estimated from a letter. According to APS News, William Boreel, a Dutch diplomat and old friend of the Janssen family, wrote about the origin of the microscope in the 1650s. On this basis, historians regard it as an invention of the early 1590s.

Nothing can be said with certainty about the inventor. Some historians credit both the Janssen family and Hans Lippershey, of telescope fame, as having invented it separately at the same time.

A tube, two lenses and three to nine times

What were these first microscopes like? According to APS News, a Janssen-style microscope was a tube standing on a brass tripod. It had a concave lens (curved inwards) at one end and a convex lens (curved outwards) at the other. This pair of lenses bent light and made an object look three to nine times larger.

By today’s standards, this is very modest magnification. But the key point was that two lenses worked together instead of one. That is why it is called a “compound” microscope. One lens forms a large image of the object, and the other enlarges that image further and carries it to the eye. The microscopes in today’s laboratories also work on the same basic principle.

APS News writes that none of Janssen’s early microscopes survives. However, a museum in Middelburg holds a microscope dated 1595 that bears Janssen’s name. It has three tubes that slide into one another and is held in the hand. When fully extended, it magnifies up to ten times.

Galileo’s “little spectacles”

Galileo Galilei, the Italian scientist who built telescopes, soon realised that the same pairs of lenses could also magnify nearby objects. According to the Museo Galileo in Florence, Galileo mentioned in his book Il Saggiatore, published in 1623, a telescope that had been modified to see very close objects. His early microscopes also had one concave and one convex lens fitted in a rigid tube.

The instrument had no single name. In Italian, it was called “occhialino”, meaning “little spectacles”, and was given some other names. According to the Museo Galileo, in 1625 Johannes Faber, a physician and botanist who was a member of a learned society in Rome, gave it the name “microscope”. The word is made of two Greek parts: “micro”, meaning small, and “scope”, meaning to see. In Urdu it is called “khurdbeen”: “khurd” means small and “been” means one who sees.

Better lenses, deeper sight

The early microscopes magnified very little. So in the next century, scientists and craftsmen worked to improve them. According to APS News, the English scientist Robert Hooke was among the first to make notable improvements to the design. His microscopes were built by Christopher Cock, an instrument maker of London, but flaws in their lenses blurred the image.

Interestingly, the sharpest sight came from a simple instrument. According to APS News, Antonie van Leeuwenhoek of Delft magnified objects up to 270 times with just one tiny lens. The discoveries of Hooke and Leeuwenhoek, the cell and microorganisms, are the subject of coming parts of this series.

A small tube, a big impact

The three-to-nine-times tube that came out of the Middelburg shop changed the course of biology, chemistry and physics. According to APS News, the twentieth century brought microscopes that keep the image clear even when the magnification is changed. Later, glowing dyes and digital images made them more powerful still. Today, when a student in a school laboratory in Quetta looks at an onion skin under a microscope for the first time, he or she is looking through the same window that two lenses opened more than four hundred years ago.