710 BC: The ancient Nimrud lens is crafted in Mesopotamia. It seems it was used as an ornament rather than a magnification device.

In the 1st Century, Roman philosopher Seneca observes that a sphere filled with water can magnify. My fish look enormous, he said. This really didn’t further magnification and revealed the forgetful Seneca did not feed his fish correctly.

Hard to believe, it took until the 13th Century for Italian spectacle makers to grind some curved glass lenses. It was to keep old half-blind Luigi from falling over the equipment in the factory.
In 1590, Dutch spectacle-makers Hans and Zacharias Janssen invented the first microscope by placing multiple lenses inside a sliding tube. Hans looking at an ant, nearly fainted. Zacharias went out to capture a ladybug instead. Getting a big influx of orders for spectacles made them set aside their discovery.
In 1609, Galileo Galilei hears of the Dutch experiments. News did not travel fast in Europe.
He added a knob for focusing the device. He called it a “microscope with a new knob”.
In1665, Robert Hooke examined razor-thin slices of cork. He calls the tiny, honeycomb-like structures he sees, “cells”.
1674: Antonie van Leeuwenhoek, a self-taught Dutch scientist, was a busybody. His curiosity brought him to make a microscope. He looked at all kinds of things. He had been observing cloth for quality and found it rather boring. He played around making lenses to improve magnification. As his lenses improved, he looked at some local pond water. His observations brought disbelief as he told of tiny animals living in there unseen. He called them dierkens. He was Dutch, you know.

His curiousity was unlimited.

Van Leeuwenhoek kept his method of making lenses quiet but introduced his work to his friend, the prominent Dutch physician Reinier de Graaf
The Royal Society in London published the groundbreaking work of an Italian lensmaker in their journal. De Graaf gave a ringing endorsement of Van Leeuwenhoek’s microscopes which, he claimed, “far surpass those which we have hitherto seen”. In response, in 1673, the society published a letter from Van Leeuwenhoek that included his microscopic observations on mold, bees, and lice. He left out bacteria because no one would believe it.

De Graaf urged him to be more confident in his work. By the time Van Leeuwenhoek died in 1723, he had written many letters to the Royal Society, detailing his findings on his work with his microscope. He only wrote letters in Dutch, never Latin.

Henry Oldenburg, attempted to translate the Dutch scribbling of Van Leuwenhoek
He first to use the word animalcules to translate the Dutch words that Leeuwenhoek used to describe microorganisms
The Van Leeuwenhoek relationship with the Royal Society became severely strained. Why? He sent the Royal Society a copy of his first observations of microscopic single-celled organisms in 1676. The existence of single-celled organisms was entirely unknown. His observations of microscopic life were initially met with great skepticism. There was a lot of harrumphing at the Royal Society, to be sure.

Thanks a lot De Graff, Leeuwenhoek was heard to say.
Eventually, in the face of Van Leeuwenhoek’s insistence, the Royal Society arranged for Alexander Petrie, a person they thought much of to determine whether Van Leeuwenhoek was a nutcase or not. He was in Dutch with the society.

Well, finally in 1677, Van Leeuwenhoek’s observations were fully acknowledged by the Royal Society.

Van Leeuwenhoek was even elected to the Royal Society in 1680. He did not attend the induction ceremony in London, nor did he ever attend a Royal Society meeting.
By the end of the seventeenth century, Van Leeuwenhoek had a virtual monopoly on microscopic study and discovery.
A contemporary Robert Hooke, an early microscope pioneer, bemoaned that the field had come to rest entirely on one man’s shoulders. Now he was published in the journal of the Royal Society of London. He was visited over the years by many notable individuals who gazed at the tiny creatures under his microscope.

Some of these were famous people like John Locke , James II of England , William III of Orange, Mary II of England and the Bishop of Cranberry.
In 1697, Van Leeuwenhoek visited the Tsar Peter the Great presenting the Tsar with an “eel-viewer”, so Peter could study blood circulation. To the disappointment of people, Van Leeuwenhoek never revealed how he made lenses for the microscopes he relied on for his discoveries.

His discoveries included:

Observing blood and skin.

Although others looked at things microscopic,
Leeuwenhoek was the first to recognize what they were, like red blood cells. Leeuwenhoek described their movement within the vessels:

“If we now plainly perceive that the passage of the blood from the arteries into the veins of the tadpole is not performed in any other than those vessels, which are so minute as only to admit the passage of a single globule at a time, we may conclude that the same is performed in like manner in our own bodies and in those of other animals.”

In 1675, he was studying a variety of minerals, especially salts, and parts of plants and animals.
Leeuwenhoek diligently began to search for his animalcules. He found them everywhere: in rotten water, in ditches, on his own teeth.

“Although I am now fifty years old,” he wrote to the Royal Society, “my teeth are well preserved, because I am in the habit of rubbing them with salt every morning.”
In 1687, Van Leeuwenhoek reported his research on coffee beans and their oil.
He studied rainwater, the seeds of oranges, wolves in sheep’s clothing, the eye of a whale, the blood of fishes, the skin of elephants.
His curiousity was endless.

Van Leeuwenhoek even diagnosed his own illness. He suffered from a rare disease, now called Van Leeuwenhoek’s disease, not surprisingly. He died at the age of 90, in 1723.

British microscopist Brian J. Ford thought that Leeuwenhoek remained imperfectly understood. The popular view was that his work was crude and undisciplined since he was not formally trained.
British biochemist Nick Lane
wrote that he was “the first even to think of looking—certainly, the first with the power to see.” His experiments were ingenious, and he was “a scientist of the highest calibre”. He was attacked unfairly by people who envied him or “scorned his unschooled origins”, not helped by his secrecy about his methods.

Leeuwenhoek was undoubtedly one of the greatest advancers of knowledge of the micro-world in history. He faced non-believers and convinced them that his world of little animals existed.

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