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A Brief History of Light Microscopy - From the Medieval Reading Stone to Super-Resolution

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The 1st lens is put above the specimen, it is called the objective lens.  It enlarges the picture of the specimen.  Some microscopes have multiple.

The 2nd lens is called the ocular lens, and it magnifies the image EVEN further.

They have a few problems such as detail and resolution limitation of the images.  And usually, you must use a chemical dye to see the living cells.

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From the medieval reading stone to super-resolution

The history of microscopy begins in the Middle Ages. As far back as the 11 th century, plano-convex lenses made of polished beryl were used in the Arab world as reading stones to magnify manuscripts. However, the further development of these lenses into the first microscopes cannot be attributed to any one person. It took the ideas and designs of many scientists and scholars to produce instruments capable of strong magnification.

First magnifying instrument built by a spectacle maker

Although the idea of magnifying objects with two glass lenses positioned one in front of the other originated as early as the beginning of the 16 th century, it was some time before such an instrument was built. The Dutch spectacle maker Hans Janssen and his son Zacharias are generally credited with creating these compound microscopes. The two of them built what was probably the first compound microscope in the last decade of the 16 th century. It had a magnification that could be adjusted between 3 and 9x.

But other scientists applied themselves to building these magnifying instruments, too. In 1609, Galileo Galilei made a microscope by converting one of his telescopes. It had a diverging lens as an eyepiece and a converging lens as an objective. An early microscope made of two converging lenses was presented around 1620 by the astronomer Cornelius Drebbel. However, it was apparently not Drebbel's own idea but that of Johannes Kepler.

Hooke's Micrographia

It was the English universal scholar Robert Hooke who really put the relatively new science of microscopy on the map.

In 1667 he was the first to publish a fundamental work on the subject called "Micrographia". The drawings it contained of his observations with the microscope made the microcosm accessible to a wider public. Some of the pictures he presented are 50x magnifications.

Hooke obtained his microscopes from the instrument maker Christopher Cock from London. He improved them by combining the customary oil lamp illumination with a cobbler's ball, a glass flask filled with water that focused the light on the specimen to illuminate it more homogeneously. However, Hooke had major problems with image aberrations that became even more pronounced when two lenses were used.

Living cells observed for the first time by a draper

The highest microscope magnifications for quite a time to come were achieved by the Dutchman Antonie van Leeuwenhoek, who lived from 1632 to 1723. The cloth merchant, for whom microscopy was only a hobby at first, managed to magnify objects more than 200 times with his microscopes. Instead of working with compound microscopes like Hooke, however, he used microscopes that only had one single lens. He thus avoided the problem Hooke had had with the additive effects of aberrations of two lenses. However, one of the disadvantages of only using one lens was that the instrument had to be held up close to the eye.

Even today, no one really knows exactly how Leeuwenhoek managed to make such good lenses that were almost free of surface inclusions and defects and allowed such high magnifications. When he died at the age of 91 in 1723, his knowledge of lens making died with him. Thanks to the good magnification of his microscopes, Leeuwenhoek was the first to observe living and moving cells such as bacteria and spermatozoa.

As microscopes were primarily considered a pastime for the rich and their potential value for science was not recognized, several decades passed without any further pioneering technical improvements. Not until later in the 18 th century were achromatic microscope objectives built that prevented major chromatic aberrations, thereby reducing the loss in resolving power caused by lens imperfections. One of the reasons it took so long for achromatic objectives to be invented was a statement by Isaac Newton. Newton, already a famous natural scientist, had erroneously maintained in 1666 that achromatization was not possible.

Abbe's law of diffraction and Koehler illumination

At the beginning of the 19 th century, Joseph von Fraunhofer was able to reduce image aberrations even further by making considerable improvements to the quality of glass used for microscope optics. In the mid 19 th century, the Italian Giovanni Amici pressed ahead with the development of water and oil immersion objectives. Finally, in 1873, Ernst Abbe provided the scientific basis for producing powerful microscopes in series. Before that, microscope lenses had always been made by trial and error and not, as from now on, by calculated optics. At the same time, however, Abbe predicted that the maximum resolving power of light microscopes was limited to 200 nm at the most. As well as the basis for calculating microscope optics, Abbe also came up with improved oil immersion objectives and an optimized illumination device over the next few years. Only a few years later, August Koehler developed "Koehler illumination", which standardized microscope illumination and remains a generally accepted illumination procedure to this day.

Great progress achieved by new contrast methods, fluorescence and confocal technology

The first half of the 20 th century saw a many discoveries that laid the foundation for modern microscopy techniques. Most importantly, fundamental principles were established for fluorescence microscopy and related technologies such as two- and multi-photon microscopy. Another development that revolutionized the world of microscopy was the construction of the first phase contrast microscope by Fritz Zernike in 1941. A few years later, at the beginning of the second half of the 20 th century, Georges Nomarski invented another microscopic contrast technique called differential interference contrast, which, like phase contrast, is still in widespread use today.

An important step for the further development of fluorescence microscopy was the discovery of the green fluorescing protein GFP. It comes from the jellyfish Aequorea victoria and was described for the first time by Osamu Shimomura in 1961. In the nineteen nineties, Douglas Prasher und Martin Chalfie managed to express GFP outside the jellyfish for the first time so that it could be used as a marker for other proteins. Many fluorescence techniques were developed and improved in the following years that still play an important role in modern microscopy, such as FRAP (Fluorescence Recovery after Photobleaching) and TIRF (Total Internal Reflection Microscopy).

In 1957, Marvin Minsky applied for the first patent for confocal microscopy. At first, this was largely ignored by the scientific community. After the method had been improved with laser technology, however, it was finally generally accepted and became a very popular technique.

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The history of microscopy begins in the Middle Ages. As far back as the 11th century, plano-convex lenses made of polished beryl were used in the Arab world as reading stones to magnify manuscripts. However, the further development of these lenses into the first microscopes cannot be attributed to any one person.

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Light Microscope: Functions, Parts and How to Use It - YaleTools

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Most familiar to most.

Usually in educational and work settings.

A compound light microscope!  It allows light to go through the specimen and use two lenses to form an image.

The article provided is not completely necessary to read.

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A light microscope is a biological laboratory equipment, which uses visible light to detect and magnify very small objects.

A light microscope uses a lens to focus light on a specimen, magnifying it to produce an image. The specimen is usually placed close to a microscopic lens.

Microscopic magnification varies greatly depending on the type and number of lenses that make up the microscope. Depending also on the number of lenses, there are two types of microscope:

Simple light microscope: it has a low magnification because it uses a single lens.

Compound light microscope: has a higher magnification than a simple microscope because it uses at least two sets of lenses, an objective lens and an eyepiece.

Light Microscope Function

The function of the light microscope is based on its ability to focus a beam of light through a very small and transparent specimen, to produce an image.

The image is then passed through one or two lenses for magnification to view. The transparency of the specimen allows for easy and fast light penetration. Specimens can vary from bacteria to cells and other microbial particles.

The principle of a light microscope is to visualize an image by using the ability of the lens to bend light and focus it on the specimen is what makes up the image.

When a ray of light passes from one medium to another, it is bent at the interface causing refraction.

The bending of light is determined by its index of refraction, which is a measure of how much a substance slows down the speed of light. The direction and magnitude of the bending of light is determined by the refractive index of the two mediums that make up the interface.

Light Microscope Parts

The ocular lens is part of the optical system, which is directed at the user of the microscope. This is the part that has at least one or more lenses.

The function of the ocular lens on a microscope is to convert the enlarged real-middle image from the objective into an enlarged virtual-image. The size of the incoming light cone will be adjusted to the size of the human eye.

Body tube is part of the microscope that serves to accommodate the lens system that enlarges the specimen.

Objective revolvers are used in microscopes with multiple objective lenses, which have different magnification factors. By rotating the revolver, you can select the lens with the desired level of magnification.

Arm is a holder connected to all components that function as a support for the microscope so that the microscope can be used properly.

The stage clip acts as a holder for the object plate and ensures that it doesn't fall out of place accidentally.

The microscope stage is the part that serves to place the object plate with a cover glass on it. By sliding the platen, you can select the part of the object you want to view.

Higher quality microscopes sometimes use a cross table as a table. This makes it possible to slide the object plate through the adjusting screw.

Cross table is a technical term which is a table construction that is mounted into a rail system. There is an adjustment screw, which can be used to move the table with great ease and precision.

The screw is equipped with a measuring scale, so you can easily find a specific point of the object again.

Condenser serves to bind the rays from the light source, so that the light can be projected on the object. Thus, every part of the object will be illuminated at the same brightness level.

The diaphragm usually consists of one or two lenses. These lenses fractionate the light and all the rays leave as parallel beams. Aspherical lenses ensure that no aberrations occur.

This will guarantee better image quality. The production cost of the diaphragm is more expensive than the normal lens. You can tell which microscope is better by looking at it from this diaphragm.

Another way to reflect light perfectly is to use an optical filter with a dielectric surface. Bragg mirror which is a kind of thin mirror with a refractive index that can be high and low.

Fine Adjustment Knop & Coarse Adjustment Knop

This mirror allows for very high-quality light beam reflection, which makes the image sharper later on and proactively reduces lens error.

With fine focus you can adjust the distance between the object and the objective, to achieve the required sharpness. Fine focus works by moving the lens smoothly.

Like fine focus, coarse focus also moves the stage to adjust the difference between the object and the objective. The function of the coarse focus is to capture the exact distance roughly and quickly. Optimal sharpness can be adjusted to finer roughness afterwards.

Early microscopes used concave mirrors to reflect light on objects. Then, they used light bulbs. Most microscopes operate with an LED light. The job of the light source is to illuminate the object evenly.

Base is the very bottom. Base serves to accommodate all parts of the light microscope.

How to Use a Light Microscope

Start with a low lens and a clean slide. The microscope stage should be lowered as low as possible.

Center the slide so that the specimen is under the objective lens.

Use the coarse adjustment knob to get a general focus. Then slowly move up the stage until focus is achieved.

Use the fine adjustment knob to get clear focus.

Center the specimen on a low plane before moving it to a medium plane.

Switch the objective lens to medium and focus using a fine adjustment. If you can't see the specimen at this point, return to the low plane and re-center.

Once you've focused and centered on the medium power, you can move it to even greater magnification.

To use a light microscope, you can follow the steps below carefully.

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Light Microscope: Functions, Parts and How to Use It - YaleTools

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A light microscope is a biological laboratory equipment, which uses visible light to detect and magnify very small objects. A light microscope uses a lens to focus light on a specimen, magnifying it to produce an image. The specimen is usually placed close to a microscopic lens.

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A microscope shows an enlarged picture of something.

Most of them use lenses to magnify the image using electrons or light.

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After Van Leeuwenhoek, more observations made it clear that cells are the basic units of life.

In 1838, Matthias Schleiden, a German botanist, made the conclusion all plants are made of cells.  The next year, Theodore Schwann, a German biologist, stated that all animals are made of cells.

In 1855, German physician Rudolf Virchow concluded that new cells can be produced only from the division of existing cells.  It confirmed an early suggestion made by German Lorenz, in 1805.

These discoveries are summarized by the cell theory.

All living things are made up of cells.

Cells are the basic units of structure and function in living things.

New cells are produced from existing cells.

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Scientists once thought that life spontaneously arose from nonliving things. Thanks to experimentation and the invention of the microscope, it is now known that life comes from preexisting life and that cells come from preexisting cells. 

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History of the Cell: Discovering the Cell

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“Seeing is believing.”

People didn’t know about cells until a microscope was made in the late 1500s by eyeglass makers.

In 1665, Robert Hooke used a early microscope to look at a piece if nonliving cork, a plant material.

They seemed to have “chambers,” which looked like little rooms and in turn, Hooke called them cells.

In Holland, Anton van Leeuwenhoek used a single lens microscope to observe pond water, revealing many tiny living organisms everywhere in the water.

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Thursday, May 23, 2019

Although they are very different on the outside, on the inside, an elephant, a sunflower and an amoeba are all made of the same building blocks. From the single cells that make up the simplest organisms to the trillions of cells that make up the complex structure of the human body, each and every living being on Earth is made of cells. This idea is part of the cell theory and is one of the central concepts of biology. Cell theory also states that cells are the basic building blocks of living organisms and that all cells come from other cells. This knowledge is foundational today.

Scientists did not always know about cells, though. The discovery of the cell would not have been possible if not for advancements to the microscope. Interested in learning more about the microscopic world, scientist Robert Hooke improved the design of the existing compound microscope in 1665. His microscope used three lenses and a stage light, which lit up and enlarged the specimens. These advancements allowed Hooke to see something amazing when he placed a piece of cork under the microscope. To him, the cork looked as if it was made of tiny pores, which he came to call "cells" because they reminded him of the cells in a monastery.

Not long after Hooke's discovery, Dutch scientist Antonie van Leeuwenhoek detected other hidden, tiny organisms called bacteria and protozoa. It was unsurprising that van Leeuwenhoek would make such a discovery. He was a master microscope maker and perfected the design of the simple microscope, which only had a single lens. The single lens enabled it to magnify an object by around 200 to 300 times its original size. What van Leeuwenhoek saw with these microscopes was bacteria and protozoa, but he called these tiny creatures "animalcules."

Van Leeuwenhoek became fascinated. He even took a look at the plaque between his teeth under the microscope. In a letter to the Royal Society, he wrote, "I then most always saw, with great wonder, that in the said matter there were many very little living animalcules, very prettily a-moving."
Both Plants And Animals Have Cells
In the 19th century, biologists began taking a closer look at both animal and plant tissues. Scientists could easily tell that plants were completely made up of cells. That's because plant cells have a layer on the outside called a cell wall. However, this was not so obvious for animal cells, which lack a cell wall. Many scientists believed that animals were made of "globules."

German scientists Theodore Schwann and Mattias Schleiden studied cells. Schwann studied animal cells, and Schleiden studied plant cells. These scientists identified key differences between the two cell types and put forth the idea that cells were the simplest units of both plants and animals.

However, Schwann and Schleiden misunderstood how cells grow. Schleiden believed that cells were "seeded" by the nucleus at the center and grew from there. Similarly, Schwann claimed that animal cells "crystalized" from the material between other cells. Eventually, other scientists began to uncover the truth. Another piece of the cell theory puzzle was identified by Rudolf Virchow in 1855. He stated that all cells are generated by existing cells.
Cells Carry Information To The Next Generation
At the turn of the century, attention began to shift toward cytogenetics. This field of science aimed to link the study of cells to the study of genetics, which focuses on genes. Genes tell the body how to grow and work. Chromosomes are like threads that carry genes and sit inside of cells. In the 1880s, Walter Sutton and Theodor Boveri identified the chromosome as being responsible for passing down genes from one generation to the next. The discovery forever linked genetics and cytology. Later discoveries further confirmed and solidified the role of the cell in passing characteristics down from one generation to another. One famous example is James Watson and Francis Crick's studies on the structure of DNA.
The Science Of Stem Cells
The discovery of the cell continued to be important for science 100 hundred years later, with the discovery of stem cells. Stem cells are simple cells that have yet to develop into more specialized cells. Scientists began to find and take out stem cells from unborn mice in the 1980s. In 1998, James Thomson isolated unborn human stem cells and developed cell lines. His work was then published in an article in the journal Science. It was later discovered that adult tissues, usually skin, could be reprogrammed into stem cells and then form other cell types. These cells are known as induced pluripotent stem cells. Stem cells are now used to treat many conditions, such as Alzheimer's and heart disease.
The Building Blocks Of All Living Things
The discovery of the cell has been far more important for science than Hooke could have ever dreamed in 1665. It gave us an understanding of the building blocks of all living organisms. It has also led to advances in medical technology and treatment. Today, scientists are working on personalized medicine, which would allow us to grow stem cells from our very own cells and then use them to understand disease processes. All of this and more grew from a single observation of the cell in a cork.

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History of the Cell: Discovering the Cell

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Thursday, May 23, 2019 Although they are very different on the outside, on the inside, an elephant, a sunflower and an amoeba are all made of the same building blocks. From the single cells that make up the simplest organisms to the trillions of cells that make up the complex structure of the human body, each and every living being on Earth is made of cells.