It has taken science a number of centuries to reach this point, but we finally have the light microscope. The journey to develop such devices travels all the way back to the creation of crude lenses, and finally ended when scientists perfected the lens and were able to pair it with a light source. You’ll find them in classrooms and research labs everywhere these days because of their incredible ability to show the minutest details of miniscule objects and specimens with complete clarity, and they’re fairly affordable to boot.
As mentioned, the history of light microscopes dates all the way back to the invention of the glass lens. No, they didn’t have fluorescent lights in the 16th century. However, it was Zaccahrias Janssen who first came to understand the compounding properties of lenses placed in a tube in 1590. Galileo, nearly 20 years later, would then improve upon the design. From there, Anton van Leeuwenhoek’s crafted a basic microscope that relied on a single lens that was finely-tuned to provide magnifications of up to 270 diameters. By using a total of three lenses, he was even able to view bacteria, water drops, blood capillaries and plants.
That was then. This is now. Today’s light microscopes come in several varieties. Compound microscopes utilize multiple lenses to achieve a magnifying power of 1,000 to 2,000 times. This allows users to clearly see things as tiny as cellular components.
Fluorescence microscopes are also very popular these days. These units are serious business and are usually only found in labs. They put out light with a longer wavelength that gives a level of clarity that is not otherwise possible to achieve.
How The Microscope Changed The World
Microscopes are invaluable research tools that provide researchers and students with the ability to view the smallest of objects through a lens that blows them up. Using this technology, anyone can see things that would otherwise be far too tiny to study.Those who use a microscope regularly tend to view both organisms that are helpful and harmful to man. In this way, they have been able to learn much about how microscopic organisms affect humans.
None of their work would have been possible without the invention of the lens.
Its origins stretch back to the Netherlands in 1590, but the true breakthrough came in 1625 when Galileo got to work. Despite being nearly 400 years old, these essential research tools are, as mentioned, still in widespread use to this day. In fact, just about every high school, college, university, hospital and research laboratory across the world has microscopes on hand these days.
They were first put to use for analytical purposes back in the 1660s in England and Italy, where researchers studied lung structure. A few years later, spermatozoa and red blood cells were discovered by Antoni van Leeuwenhoek through the use of a microscope. Advancements continued to come at a decent pace for the next few hundred years. But the next major breakthrough came along in 1955 when the electronic microscope was invented. The illumination provided by this kind of scope allowed scientists to understand the many layers of cells and provided them with a means to watch them grow.
Microscopes have drastically changed the worlds of education, science and medicine. Thanks to these fascinating devices, man has been able to discover the wonders of the human body and study myriad ways to improve and protect it with medicinal treatments.
Different types of microscopes
How many different types of microscopes are there? More than you probably thought. I tried to research a list of different types, based on the physical principle used to make an image. Of course, one could also classify the microscopes based on their area of application, their cost, their versatility or any other aspect. These classification systems do have a problem: In this case one one type of microscope can be allocated to several groups, and the system becomes “messy”.
Optical Microscopes: These microscopes use visible light (or UV light in the case of fluorescence microscopy) to make an image. The light is refracted with optical lenses. The first microscopes that were invented belong to this category. The price of optical microscopes varies from very cheap to nearly unfordable (for the private person, at least). Optical microscopes can be further subdivided into several categories:
- Compound Microscope: These microscopes are composed of two lens systems, an objective and an ocular (eye piece). The maximum useful magnification of a compound microscope is about 1000x.
- Stereo Microscope (dissecting microscope): These microscopes magnify up to about maximum 100x and supply a 3-dimensional view of the specimen. They are useful for observing opaque objects.
- Confocal Laser scanning microscope: Unlike compound and stereo microscopes, these devices are reserved for research organizations. They are able to scan a sample also in depth. A computer is then able to assemble the data to make a 3D image.
X-ray Microscope: As the name suggests, these microscopes use a beam of x-rays to create an image. Due to the small wavelength, the image resolution is higher than in optical microscopes. The maximum useful magnification is therefore also higher and is between the optical microscopes and electron microscopes. One advantage of x-ray microscopes over electron microscopes is, that it is possible to observe living cells.
Scanning acoustic microscope (SAM): These devices use focused sound waves to generate an image. They are used in materials science to detect small cracks or tensions in materials. SAMs can also be used in biology where they help to uncover tensions, stress and elasticity inside biological structure.
Scanning Helium Ion Microscope (SHIM or HeIM): As the name suggests, these devices use a beam of Helium ions to generate an image. There are several advantages to electron microscopes, one being that the sample is left mostly intact (due to the low energy requirements) and that it provides a high resolution. It is a relatively new technology and the first commercial systems were released in 2007.
Neutron Microscope: These microscopes are still in an experimental stage. They have a high resolution and may offer better contrast than other forms of microscopy.
Electron Microscopes: Modern electron microscopes can magnify up to 2 million times. This is possible, because the wavelength of high energy electrons is very small. At the same time, the high energy electrons are pretty tough on the sample being observed. It may take a long time to completely dehydrate and prepare the specimen. Some biological specimens also need to be coated with a very thin layer of a metal before they can be observed.
- Transmission electron microscopy (TEM): In this case, the electron beam is passed through the sample. The result is a two dimensional image.
- Scanning electron microscopy (SEM): Here the electron beam is projected on the sample. The electrons do not go through the sample but bounce off. This way it is possible to visualize the surface structure of the specimen. The image appears 3 dimensional.
Scanning Probe Microscopes: It is possible to visualize individual atoms with these microscopes. The image of the atom is computer-generated, however. A small tip measures the surface structure of the sample by rastering over the surface. If an atom projects out of the surface, then a higher electrical current will flow through the tip. The amount of current is proportional to the height of the structure. A computer will then assemble the position data of the tip and the current to generate an image.
Conclusion: Microscopes can be classified based on the physical principle that is used to generate an image. Different microscopes visualize different physical characteristics of the sample (eg. elasticity can be visualized with acoustic microscopes). Image contrast, resolution (which determines magnification) and destructiveness of the sample are other relevant parameters.