The Parts of a Microscope

44202b000s0bc86pt01The microscope is perhaps one of the world’s greatest inventions. It is an essential tool that is widely used by medical professionals and scientists to study objects that appear to be invisible to the naked eye. This is because, the smallest object visible to the human eye is less than 100 micrometres.

Microscopes have helped mankind study a lot of microscopic organisms that, although are invisible to the naked eye are all around us. As an example, human body parts such as organs and other tissues are made of cells that can only be seen or studied using a microscope. It has also allowed scientists and medical experts to know more about other living organisms such as bacteria and viruses that cause many diseases that affect the lives of everyone in the world.

With the invention of the microscope, we were introduced to an unknown world, which eventually proved to be beneficial to everyone. We were able to understand what living and non-living things are made of and how they affect the world that we live in.

Understanding the Parts of a Microscope and Their Functions

The modern microscope didn’t happen overnight, in fact, it developed over a millennia and Robert Hooke was developed the compound microscope in the 1600s. Read more about the history of microscopes here.

Thanks to these gradual developments, today’s microscopes continue to help scientists and students around the world learn and make new discoveries about the natural world.

However, these sophisticated pieces of kit aren’t that straightforward to use until you understand how each microscope part works and what it’s purposes is. Therefore, by studying the microscope diagram below and the brief explanation of the key parts, you will hopefully broaden your understanding and learn how to use your microscope with confidence.



  1. Eyepiece lens and eyepiece tube – this part is the one on top where users view or look through the device; the eyepiece tube is the tube that connects the ocular lens to the device itself
  2. Objective lens – generally, a microscope contains three to four objective lenses with 4X, 10X, 40X, and 100X magnifying power; the role of the lens is to focus light rays at a specific place called the focal point. The distance between the center of lens and the focal point is the focal length and the power or strength of the lens is related to focal length, i.e. the shorter the focal length, the more magnification.
  3. Tube – this part of the microscope is the one connecting the eyepiece or the top lens to the objective lens section
  4. Base – the base is the bottom part of the microscope that supports the weight of the device
  5. Arm – the arm of the microscope attaches the tube to the base and provides structural support to the device; it is where users hold the microscope as well when they need to carry it from one place to another – one hand to hold the arm and the other hand under the base for better support
  6. Illuminator – an illuminator is a steady source of light used instead of a mirror; it normally uses low-volt bulb of 100 volts; if your microscope uses a mirror, then it is expected to utilise light from the surrounding environment
  7. Stage or platform – this part is where doctors or scientists put the microscope slide with samples for analysis; it normally has clips that prevents a slide from moving while it is being viewed by the user from the eyepiece part; the slide can be moved manually while it is being viewed or it can be moved mechanically if you are using a microscope with a mechanical platform; this is done by rotating the knobs which can either move the slide sideways or upward and downward
  8. Stage clips – as discussed above, this part of the microscope prevents the microscope slides from moving or falling
  9. Rotating turret or nosepiece – this part has 2 or more objective lenses that allows users to rotate the lenses based on the power that they need to use
  10. Rack stop – this is the part that moves or adjusts the objective lenses closer or away from the platform or microscope slide; this has to be used properly as moving the objective lenses too close to the platform or slide can break the slide or damage the objective lens
  11. Condenser lens – a condenser lens collects the light coming from the illuminator and focuses it on the slides or the specimen being viewed and analyzed; a condenser lens provides a crispier or a clearer view of the specimen than the ones with no condenser lens for better resolution up to 1000 times magnification. In more advanced microscopes an Abbe condenser is used; this provides a cone of light to the object of correct size and angle.
  12. Iris or diaphragm – the iris or diaphragm regulates the light that reaches the specimen for better view and analysis
  13. Coarse adjustment knob – this knob is located on the microscope’s arm; this is used to adjust the slide with specimen to put it in the best position for proper viewing; a user would normally turn the knob several times until he gets the image that he wants; the coarse adjustment knob should be turned slowly and carefully to get the best view and prevent any damages to it
  14. Fine Adjustment Knob – this is part of the coarse adjustment knob which is also used to get a better view of the microscope slide with the specimen being analyzed
  15. Power switch – this is used to turn on or off the light coming from the illuminator

How Microscopes Work and How to Use Them?

Basic Principles of Light 

Light is a wave and the amplitude determines the brightness, while wavelength determines the colour and frequency is number of waves per second. The size of an image is determined by the angle of light entering the eye, and the glass lens used in microscopes slows the light. In technical terms, the wavelength becomes shorter and light bends, this is called refraction.


The smallest distance that can be distinguished between two points is called resolution. Resolution is equal to 0.6 x wavelength/numerical aperture, therefore, the shorter the wavelength the greater the resolution. However, resolution is limited by the numerical aperture, which is the light gathering capacity of the lens.

How to use a Microscope – Basic Steps: 

  1. Fully open field and condenser diaphragms and focus on specimen using x10 objective
  2. Fully close field diaphragm and adjust the condenser and focus so edges are as sharp as possible
  3. Use screws at front of condenser to centre field diaphragm and open field diaphragm to fill view
  4. Remove eyepiece and close down aperture diaphragm, open the diaphragm to fill approx one third of view
  5. Replace the eyepiece and alternate between the different eyepieces as necessary

Final Words 

There was a part in our history when we were not aware of the tiniest living organisms in the planet. We did not pay attention to them as we did not know they existed in the first place. But the invention of the microscope changed this dramatically and we have gone a long way since then, discovering microbes and the organelles of the mammalian cell. They truly are a remarkable feat of human engineering and scientific discover.