A Short History of the Microscope
   Historians disagree as to who invented the microscope. Spectacles were known in  Florence, Italy in the late 1200's.  In the late 1500's, Dutch spectacle-makers began experiment with lens.  In 1608,  Hans Lippershey, applied for a patent on his magnifying tube which enlarged distant objects.  He reported also used variations of it to enlarge subjects near at hand.  A few months later, Italian instrument maker Galileo made his own magnifying tube, and reported, "I have seen flies which look as big as lambs, and have learned that they are covered over with hair and have very pointed nails by means of which they keep them selves up and walk on glass, although hanging feet upwards, by inserting the point of their nails in the pores of the glass."  He discovered, to his dismay, that while a telescope focused on the stars need to be only two feet long, to magnify small objects nearby required a tube two or three times that length.
   As early as 1625 a member of the Academy of the Lynxes, the physician-naturalist John Faber had a name for the new device.  "the optical tube... it has please me to call, after the model of the telescope, a "microscope," because it permits a view of minute things."
    Although many were very suspicious of  the "artificial image" produced by the telescope, it was observable that it did enlarge distant objects.   It was immediately useful.  This was not the case the microscope.  Although a greatly enlarged image of  everyday things was fascinating, no one could see any practical purpose for the microscope.  

   Robert Hooke
 In 1665, Robert Hooke published Micrographia, an enticing miscellany expounding his theory of  light and color, and his theories of combustion and respiration. It included a description of the microscope and its uses.  But  the widespread suspicion of optical illusion would plague him.  At first the "new world" he claimed to see through his lenses were the butt of ridicule, but what Galileo did for the telescope Hook did for the microscope.  Fifty-seven amazing illustrations drawn by Hooke himself revealed for the first time the eye of fly, the shape of bee's sting organ, the anatomy of a flea and louse and much more.  When his discovered the honeycomb structure of cork, he said it was made of "cells," thus coining the word. 
Three pictures from  Micrographia: stinging hairs on a nettle, a flea, and corks "cells."   At Left: his microscope. Light provided by candle and directed by a lens on to the subject.

Antonie van Leeuwenhoek
   As the years passed, an international community of science began to grow.  In 1668, the Philosophical Transactions of the Royal Society of London published an extract from an Italian learned journal telling how an Italian lens-maker, Eustachio Divini, using a microscope, had discovered "an animal lesser than any of seen hitherto."  Five years later, Henry Oldenburg, who was in London publishing the Philosophical Transactions received a letter from the Dutch anatomist Regnier de Graaf  describing the work of a Dutchman,  Antonie van Leeuwenhoek, who "has devised microscopes which far surpass those which we have hitherto seen.   Antonie sold wool, cotton and other textiles and also worked as the inspector of weights and measures. He often used low-power magnifying glasses to inspect the quality of cloth, and this awakened an interest in other things. He began grinding his own lens.    
  Unlike Hooke and others, who used a compound microscope that combined two or lenses,  Leeuwenhoek used a simple microscope, such as that shown at right. The specimen was mounted on the top of the pointer. Just above it is a tiny lens.  The specimen was viewed by holding the microscope and looking at the specimen through the other side. Leeuwenhoek eventually ground some five hundred fifty lens of which the best had a linear magnifying power of 500 and a resolving power of one-millionth of a meter.  Over a period of years, he reported his findings to the Royal Society through letters - one hundred and ninety of them.  In 1674, he filled a glass vial cold water from a nearby lake, and found" many small animalcules. He then turned his microscope on a drop of pepper water

   "I now saw very plainly that these were little eels, or worms, lying all huddled up together and wriggling just as if you saw, with the naked eye, a whole tubful of very little eels and water, with the eels squirming among one another; and the whole water seemed to be alive with these multifarious animalcules.  This was for me, among all the marvels that I have discovered in nature, the most marvelous of all; and I must say, for my part, that no more pleasant sight has every yet come before my eyes that these many thousand of living creatures seen all alive in a little drop of water, moving among one another, each several creature having its own proper motion."
     In his famous Letter 18 to the Royal Society (October 9, 1678), he concluded that "these little animals were, to my eye, more than ten thousand times smaller than the animalcule which  Swammerdam has portrayed, and called by the name of Water-flea, or Water-louse, which you can see alive and moving in water with the bare eyes.  Having discovered the world of bacteria, Leeuwenhoek declared that each had its full complement of bodily organs needed for life.  He opened the doors to microbiology, embryology, histology, entomology, botany and crystallography.