Microscopes: Technology at the Service of Science

It is not known exactly who invented the microscope but it is well known that after this invention, around the beginning of the seventeenth century, our perception of the world was very different.

Many attribute the invention of this instrument to Galileobut it was Leeuwenhoek who really perfected the instrument and used it in observing living things.

With only one glass lens, the first microscopes allowed magnifications of up to 300 times with reasonable clarity. And a whole world that was invisible to our eyes was revealed. With this very simple instrument, Leeuwenhoek studied the red blood cells and found the existence of sperm. This scientist also unveiled the extraordinary world of microbes (ie, microscopic beings), today better known as microorganisms.

Leeuwenhoek's simple microscope was enhanced by Hooke, earning another lens. In this way, even larger increases were obtained. Modern optical microscopes are sophisticated descendants of Hooke's compound microscope and far more powerful than the small instruments used by scientists in the early seventeenth century. They are equipped with 2 crystal lens systems (eyepieces and objectives) that produce image magnifications that generally range from 100 to 1000 times, thus revealing details that were previously invisible to our eyesight.

Ordinary optical microscope

Red blood cells, blood cells, viewed under an optical microscope and artificially stained. (Extension not provided)

In the light microscope, the light that reaches our eyes to form the image first passes through the object under study. Therefore, the material to be observed cannot be opaque. Often, to obtain enough translucent biological material to be well observed under the microscope, it is necessary to properly prepare the material you want to study. For this, very thin cuts are made, preferably with a ham slicer-like machine called microtome. The material to be cut receives a dehydration and paraffin embedding treatment that facilitates handling and allows very thin slices to be cut.

Electronic microscope

The electron microscope appeared in 1932 and is being rapidly improved. Most current machines allow increases from 5,000 to 500,000 times without much difficulty. The basic difference between optical and electron microscopes is that in the latter, light is not used, but electron beams. In the electron microscope there are no crystal lenses but coils, called electromagnetic lenses.

These lenses enlarge the image generated by passing the electron beam through the material and project it onto a screen where an image of more or less bright dots is formed, similar to that of a black and white television set. It is not possible to observe living material in this type of microscope. The material to be studied goes through a complex process of dehydration, fixation and inclusion in very hard special resins, which allow ultrafine cuts obtained through the glass knives of the instrument known as ultramicrotome.

Electronic microscope

Red blood cells, blood cells, viewed under an electron microscope. Note the richness of detail that this type of microscope allows. (Extension not provided)