Microscopes reveal the unseen world of things too small to be seen by the naked eye.
The microscope's roots reach back to around 100 AD, when Romans found that objects appeared larger when seen through a piece of glass that was thicker in the middle. They called those crude lenses "burning glasses," or magnifiers. Italian glass blowers began making solid glass "reading stones" about a thousand years later. A pair of Dutch eyeglass makers created the microscope around 1590 by mounting multiple lenses in a tube. That first microscope magnified about 20X, or 20 times. Other microscopes used only one lens.
Bugs, Bugs Everywhere
Many early single-lens microscopes magnified between 6X to 10X, just strong enough to give people a close look at tiny insects. Those early microscopes became known as "flea glasses" because fleas were one of the most commonly viewed and interesting insects.
Corks and Cells
Microscopic samples can be examined
New uses arose as microscopes became more powerful. In the mid-1600s the English scientist Robert Hooke used a 30X magnification device to examine a cork and discovered the cell, the basic unit of life. Hook called the lattice-like structures he saw through the microscope "cells" because they looked like the cell rooms in monasteries. He also examined sponges, feathers and bryozoan marine organisms. Hook published detailed drawings of what he saw in a book, "Micrographia," in 1665.
Fossils
Hooke was the first person to investigate fossils with a microscope. After comparing fossil shells with living shells and petrified wood with a piece of rotten oak wood, he described the process by which wood is turned to stone.
Tiny Swimming Things
The existence of bacteria was discovered in the 1600s.
In the late 1600s and early 1700s, a Dutch draper named Antony Van Leeuwenhoek developed techniques of grinding and polishing glass into better lenses. He used his lenses to make hand-held, single-lens microscopes with magnifications reaching 300X. He observed blood cells, the structure of yeast, bacteria and many tiny animals swimming in water that had appeared empty of life.
Pasteur Saves Beer
Louis Pasteur, founder of the field of microbiology, used microscopes in much of his revolutionary research in the 1800s. The French chemist is probably best known for developing the pasteurization process after he discovered that germs cause disease. He also solved a problem in breweries. By looking through a microscope at samples of French beer that had gone bad, Pasteur found rod shaped bacteria where there should have been yeast cells. He developed methods to make better beer by culturing "good" microorganisms.
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