The Beginnings

Of the five senses, the most important is sight.It aids in the process of gathering information about the environment that we are part of.However, this visual gathering is adequate only to a certain point. Beyond this point, the human unaided eye fails to help us; the amount of detail that it can provide is severely limited.In order to overcome those limitations, humans started to develop instruments like the magnifying glass, the spectacles, the telescope and the microscope.

The earliest development of the microscope can be traced back to the ancient world with the appearance of the magnifying glass, which was at that time use as a “burning glass.”The conception of the action of the magnifying glass with regards to the production of a magnified image that could supplement the human eye first appeared in the 13th century.  It was at this time that the ancestor of the microscope ancestor, the glass lens, first appeared.It was discovered by Roger Bacon in 1268.  As he tried to improve the “burning glass,” he accidentally broke a crystal sphere and made several observations through it.  This led him to the following conclusion: 

“If anyone examine letters or other minute objects through the medium of crystal or glass or other transparent substance, if it be shaped like the lesser segment of a sphere, with the convex side toward the eye, he will see the letters far better and they will seem larger to him. For this reason such an instrument is useful to all persons and to those with weak eyes for they can see any letter, however small, if magnifier enough".(Bradbury, 1968, 7)

The glass lens was initially used to correct and compensate for defects in the human eye by improving sight.Lens were incorporated into spectacles or eyeglasses between 1268 and 1289, and they improved the vision of people who had imperfect eyesight.  A writer of a Florentine manuscript dated 1299 in which he says:

“I find myself so pressed by age that I can neither read nor write without glasses which they called spectacles, newly invented, for the great advantage of the old men when their sight grows weak.” (Bradbury, 1968, 4)

It took several hundred years before anyone assembled glass lenses in a way that made distant objects appear close or small objects appear bigger.The appearance of new scientific ideas in the seventeenth century - like experimental philosophy and its beliefs that continuous experimentation and observation as well as the improvement of the senses were needed for the better understanding of nature- lead to the invention of instruments like the telescope and the microscope.

The telescope was invented in the 16^th century by a Dutch optician named Hans Lippershey.It was then improved by Galileo Galile into a great astronomical instrument that allows people to observe distant objects.With this instrument, he observed moons orbiting Jupiter, which contradicted the prevailing belief that all heavenly bodies revolved around the Earth.  This observation also confirms Copernicus' heliocentric theory. Galileo's observations helped initiate the scientific revolution that has fundamentally altered our world.

The first microscope was developed in England during the final years of the 16^th century.It is likely that the microscope was a result of alterations made to the telescope.  It is believed that the microscope was discovered by accidentally inverting a telescope, as indicated by the “account that one of the first microscopes was six feet long and had a one inch barrel with a lens at either end” (Cohen, 1).The earliest simple microscope was merely a tube with a plate for the object at one end and a lens at the other end that gave a magnification less than ten times the actual size.It had just one lens, and although it had an unappealing look, it was capable of extremely fine work like observing bacteria and single-celled animals.A couple of years later in 1597, Zaccharias Jansseen and his son, Han Jansseen, while experimenting with several lenses in a tube, discovered that a combination of two lenses in a particular fashion.  One lens was at the eyepiece of the microscope (ocular), and the second lens was near the sample to be studied (objective).  This arrangement significantly enlarges the sample under observation.It is believed that their idea on the particular fashion of their lenses was based on the reverse of a telescope, which explains why their instruments were two feet long and extremely heavy.Nevertheless, they evidently invented the forerunner of the compound microscope, which was later modified in the 17^th century by Robert Hooke.

After the Jansen invention, word traveled rapidly throughout the known world. More and more people took up the interest of observing things far smaller than could be perceived with the naked eye.By 1625, optical workshops had been set up throughout Europe.

The seventeenth century was a period of great interest in microscopy.  Some of the earliest discoveries and instrumentation were derived during this period of scientific interest.During this time, the word "microscope" was beginning to be accepted and regularly used by the members of the first "Academia dei Lincei," a scientific society that included Galileo.  However, the microscope wasn't just a scientific tool. Throughout this century and also during Victorian times, microscopes were owned by the upper class as recreational toys!

During 17th century, the first papers were published on microscopic findings.  The two most important papers were not published until 1660 and 1665, respectively, when Marcello Malpighi proved William Harvey's blood circulation theories, and Robert Hooke's wrote his "Micrographia."

Marcello Malpighi             Malpighi, Marcello (1628-94), Italian physiologist and one of the first great microscopists, made discoveries in microscopic anatomy that upset ancient medical beliefs and set the course for modern physiology.Even today, he is considered the father of embryology and early histology.

             Born in Crevalcore on March 10, 1628, Malpighi obtained a degree in medicine and philosophy at the University of Bologna in 1653.As professor of theoretical medicine at the University of Pisa, he began his microscopic observations and became strongly critical of the assumptions held in the fields of physiology and medicine.

              In 1659 he returned to Bologna.  In 1661, he made his most important discovery, describing the network of pulmonary capillaries that connect the small veins to the small arteries, thus completing the chain of circulation postulated by the English physician William Harvey.Malpighi’s microscopic observations provided crucial evidence for Harvey’s radical ideas.Until that time, the ancient belief had long prevailed that the blood was transformed into flesh on the periphery of the body.

              Among Malpighi's many other discoveries were his observations of the microscopic components of the liver, brain, kidneys, spleen, bone, and the inner, or what came to be known as the Malpighian, layer of the skin. He was the first to discover red blood corpuscles and to show that they gave blood its color. He also identified the taste buds and described the chick embryo, the development of the silkworm, and the structure of plants.

             Malpighi believed that living material was composed of minute glands that separated or mixed the body fluids. Although he misunderstood the microscopic functions of organs, he set the stage for cell theory and histology. His discoveries of the hidden workings of organisms forced physicians of the time to rethink firmly established assumptions. Although in his last years he received such honors as being named personal physician to Pope Innocent XII, his radical ideas cost him bitter and even violent opposition throughout much of his life.

Robert Hooke 

Robert Hooke (1635-1703), an English scientist and mechanical genius, was born on the Isle of Wight and educated at the University of Oxford.Hooke was also a pioneer in microscopic research and published his observations, which included the discovery of plant cells.His Micrographia was an important milestone in proving the importance of microscopy, and has granted him the title of English father of microscopy.

Hooke observed a thin slice of cork under the microscope and saw that it was mostly air, which allowed it to float, be firm, and yet compress under force.However, he also saw that there were pieces of material making up sort of like a mesh-work of supporting structures around the tiny pockets of air.Hooke named these pockets of air "cells" after the small monastery rooms they reminded him of.He had no idea that those air pockets that he called “cells” were the remains of what is now considered the primary structure of life.  The name, cell, remains until this day.

    Hooke also developed and modified the Jansen compound microscope into a more modern one, similar to the one we currently use.After the compound microscope, the next major development was in lenses. Half a century after the invention of compound microscope, both Robert Hooke and Anthony van Leeuwenhoek realized that lenses with very short focal lengths were the key to more magnification. This meant the use of double convex or spherical lenses.

This new double convex lenses improved the resolution, as well as the magnification, of the compound microscope.It was with this microscope that many discoveries in biology, especially in the area of microbiology, were made.Among the most important advances was the discovery of two infectious bacteria, tubercle and cholera bacilli, by Robert Koch. 

Hooke’s Micrographia              Robert Hooke published Micrographia in 1665. It is his most famous work and is notable for the stunning illustrations, drawn by Hooke himself.Micrographia is Hooke's most famous work, partly because of the brilliance of the illustrations, and partly because of the extent to which his observations turned out to be so far ahead of their time.

Microphagia presents several accounts of Hooke’s observations through the use of the microscope.He looked at all sorts of things (snow, a needle, a razor, etc.) with a primitive compound microscope.But his most significant observations were done on fleas and cork.He observed the fleas under the microscope and was able to observe the tiny hairs on the fleas’ bodies.On the cork he saw pores.  Upon examination of the pores, he decided to call them “cells”; however, he did not know he had just discovered plant cells.

Antoni van Leeuwenhoek           Antoni va Leeuwenhoek (1632-1723) was a Dutch maker of microscopes who made pioneering discoveries concerning protozoa, red blood cells, capillary systems, and the life cycles of insects.Born in Delft, Holland, Leeuwenhoek received little or no scientific education.However, his incredible discoveries in the field of microscopy granted him the recognition as the father of microscopy.In recognition of his discoveries, he was made a fellow of the Royal Society of England.

He was a scientific amateur and as a hobby he devised single, tiny, double-convex lenses mounted between brass plates and held close to the eye. Leeuwenhoek taught himself how to grind and polish glass into a lens with a magnification of 270X (a power that far exceeded that of early compound microscopes of 20-30X).  He used this lens to make the world's first practical microscope.His lens, unlike the lenses of the other microscope of the time, was a more pure glass instead of the poor quality, greenish glass of the day.

He confirmed and further developed the discovery by Italian anatomist Marcello Malpighi regarding capillary systems, demonstrating how the red corpuscles circulated through the capillaries of a rabbit's ear and the web of a frog's foot. In 1674, he gave the first accurate description of red blood corpuscles. In 1676, he then observed and described for the first time what he called animalcules—known today as protozoa and bacteria—in pond water, rainwater, in human saliva.  In 1677, he described the spermatozoa of both insects and humans.

Leeuwenhoek also opposed the prevalent theory of spontaneous generation, and through the use of the microscope demonstrated that granary weevils, fleas, and mussels were not created from wheat grains and sand but developed from tiny eggs. He described the life cycle of ants, showing how the larvae and pupae originate from eggs.Leeuwenhoek also observed plant and muscle tissue, and described three types of bacteria: bacilli, cocci, and spirilla. He kept the craft of making his lenses a secret, however, so that not until the improvement of the compound microscope in the 19th century were the next observations of bacteria made.

Leeuwenhoek’s microscope              Leeuwenhoek is known to have made over 500 microscopes, yet fewer than ten have survived to the present day.They all had a basic design of a simply powerful magnifying glass; it was nothing like the compound microscopes of the type use today.Compared to modern microscopes, it was an extremely simple device, using only one lens, mounted in a tiny hole in the brass plate that makes up the body of the instrument.The specimen was mounted on the sharp point that sticks up in front of the lens, and its position and focus could be adjusted by turning the two screws.The entire instrument was only 3-4 inches long and had to be held up close to the eye.

Microscope of Today 

During the 18^th and 19^th centuries, the microscope went through a time of several mechanical improvements that increased the stability and facilitated a smooth focus and magnification.Among other things developed during this time to improve the microscope was the creation of microscope stages and slides in order to place and secure the sample to be examined.  Also, the development of objective lenses improved and controlled the magnification and resolution of the sample.All these mechanical improvements were added in conjunction with the new sampling techniques that include the addition of water and chemicals to enhance the view of the sample, as well as to stain the sample lead to the production of a high quality clear image.The ability of this new microscope to create such images caught the attention of the scientific community and society in general.  The microscope became very popular once again, but this time it underwent a high-volume, low-cost, mass production.

The microscopes were still popular in the early 1900’s.  There was not much change in the fundamental basics of the microscopes during this time, however there was a standardization of the parts as a result of the high demands of supplies during the World War I.Among the first standardizations, we find that most microscopes were made out of cast-iron with a blackened finish and the eyepiece had been standardized into a short tube of 23mm diameter.There were many varieties of microscope manufactured during the 1900’s, but most of them had the same general parts as seen in the picture to the left.

In the 20^th century new developments and improvements have rendered the discoveries of the 19^th century to be very basic.The new microscopes are not only able to use light as a way of reflecting the image of the sample, but they are more versatile and capable of using electrons of high resolution power to examine a sample and reproduce its image.The versatility of the microscopes allows one to observe a sample in a 3-dimensional fashion rather than on a flat pain like the conventional microscopes.Also, the magnification power of these new microscopes is incredible; they can easily reach the 200,000x, or 10,000 times more than the earliest microscopes.

 Different types of microscopes  There are many types of microscopes, among the most important and recognizable we can find:

Compound microscope- uses two lenses, an objective lens and an ocular lens, mounted at opposite ends of a closed tube, to provide greater magnification than is possible with a single lens.The objective lens is composed of several lens elements that form an enlarged real image of the object being examined.It has a firm stand with a flat stage to hold the material examined and some means for moving the microscope tube toward and away from the specimen to bring it into focus.

Electron Microscope- uses electrons to "illuminate" an object. Electrons have a much smaller wavelength than light, so they can resolve much smaller structures.It has an electron gun that emits electrons in a vacuum, which then strike the specimen and records its image to display it in a monitor rather than through an objective lens.There are two types of electron microscopes: the transmission electron microscope (TEM), and the scanning electron microscope (SEM).Both of them work under the same basic principle, with the exception that a SEM scans the surface of a thinly sliced sample bit by bit and a TEM looks at a relatively large area of the sample all at once. Scanning electron microscopes can magnify objects 100,000 times or more.

Scanning probe microscope- uses a probe to scan the surface of a sample and provides a three-dimensional image of atoms or molecules on the surface of the object. The probe is an extremely sharp metal point that can be as narrow as a single atom at the tip.It provides detailed images of substances that can conduct electricity.In addition, it has a sensing mechanism that records the up-and-down movements of the probe and feeds the data into a computer, which creates a three-dimensional image of the surface of the sample.

*For more information of the topics try the following sources: 

	Jones, Thomas E.1995. http://www.utmem.edu/~thjones/hist/hist_mic.htm
	Bradbury S. 1967. The Evolution of the Microscope.Pergamon PressLtd, Oxford, London.
	Hooke, Robert. 1665. Michrophagia. Royal Society, London.
	Samuel H. Cohen. 1994. Seeing the Invisible: The New Microscope. Collier’s Year Book.
	Bradbury S. 1968. The Microscope: Past And Present. Pergamon PressLtd, Oxford, London.
	Ford, Brian J.  2001. http://www.sciences.demon.co.uk/whistmic.htm
	Doane, Nathaniel . 1995. http://www.otal.umd.edu/~vg/amst205.F97/vj06/project6.html
	1998 A-Z Microscope Corporation. http://www.az-microscope.on.ca/history/history.html
	http://www.ucmp.berkeley.edu/history/hooke.html

*They have been organized from top to bottom according to the quality of the scientific input  with respect to this page in particular.