Types of Microscopes | Their Uses in Biology & Research

A microscope is a device to visualize objects invisible to the naked eye. These instruments magnify the image many times to be visible to us.

The invention of the microscope has revolutionized science, medicine, and other areas where microscopic structural examination is required. Microorganisms like bacteria, fungi, protozoans, etc., were found to be the actual causes of epidemic diseases.

Types of microscope available

  1. Simple microscope
  2. Stereoscopic microscope
  3. Compound microscope
  4. Phase contrast microscope
  5. Electron microscope

With the advancement of technology, one can even get an image of the virus and minute molecular structures.

Besides, it is possible to take photographs of tissues and label the specimens by connecting them to computers. Let us see them in detail.

Simple microscope

  • It is a plain microscope with a single magnification lens like 10x.
  • It is used to visualize small, minute, and invisible objects to the naked eye.

Stereoscopic dissecting microscope

  • This microscope is commonly used to study and to identify the opaque objects.
  • It is generally used for low-power observation, dissection, etc. Its magnifying power varies from 4x to 40x or even 60x.
  • It has two objectives and two eyepieces, which help to make a 3D image of an object.

Compound microscope

Types of microscopes
  • A Compound microscope is the most commonly used microscope used in labs performing biological experiments and clinical diagnosis.
  • It has an eyepiece and 2 or 3 objective lenses. The magnification power ranges from 5x to 8x and 10x to 15x, with the magnification of the objectives ranging between 10x and 40x.
  • It examines semitransparent and translucent objects or parts of objects in thin slices.
  • Most bacteria, protozoa, and blood cells can be observed using it.

Phase contrast microscope

  • A phase contrast microscope is commonly used to study biological tissues and specimens.
  • It is also one of the most essential tools in medical research.
  • It is employed to study colorless and transparent specimens, which are usually difficult to distinguish from their surroundings.
  • These specimens or objects are commonly termed phase objects.
  • All phase contrast microscopes are not the same but work on the same principle and have five eyepieces of different magnifications, including 10x, 20x, 40x, 100x, and Bright Field (BF).

The electron microscope

  • It is an advanced microscope used to study minute particles with the help of electron beams instead of lenses.
  • It is used to study various biological and non-biological samples, like the structure of cell organelles, DNA, RNA, viruses, biopsy samples, metals, crystals, and large molecules.
  • It is one of the essential tools for biological and medical sciences as it magnifies the image of an object by 10,000,000x.
  • However, unlike other types, here one does not see the object under study with the naked eye.
  • The instrument produces images of the objects under study, and one needs to observe the pictures.
  • In the electron microscope, two lenses are present: “electrostatic” and “electromagnetic.”
  • These types help to control the electron beam, which illuminates the specimen and produces a magnified image.
Types of microscope -electron microscope
Credit: The University of Alabama (SH_Bevill_Labs)

This electron microscope is again of five different types:

  1. Transmission electron microscope (TEM)
  2. Scanning electron microscope
  3. Reflection electron microscope
  4. Scanning transmission electron microscope
  5. Low-voltage electron microscope.

Transmission Electron Microscope (TEM)

transmission electron microscope equipment in lab
Transmission electron microscope equipment in the lab
  • TEM uses a high-energy electron beam sent through a thin sample.
  • It provides a detailed picture of the internal structure of cells, bacteria, and nanomaterials at the atomic level.
  • TEMs have high resolution, typically around 0.1 nanometers, making them ideal for observing microcellular detail and molecular complexes.

Scanning Electron Microscope (SEM)

  • An SEM examines the sample using a focused electron beam.
  • Creates a detailed 3D model by detecting secondary or backscattered electrons from the specimen surface.
  • SEMs are commonly used to study surfaces and topography, biological samples, and microstructures with dimensions typically of 1-20 nanometers.

Reflection Electron Microscope (REM)

  • In REM, electrons are reflected from the surface of a sample.
  • It combines TEM and SEM features to provide surface structure and composition information.
  • In surface science, REM examines thin films, crystalline surfaces, and other materials where surface properties are important.

Scanning Transmission Electron Microscope (STEM)

  • STEM combines the functions of TEM and SEM.
  • It requires an electron beam focused on the sample to detect diffuse and scattered electrons.
  • STEM is used for high-resolution imaging and chemical analysis at the atomic scale, making it valuable for materials science and nanotechnology research

Low-Voltage Electron Microscope (LVEM)

  • As the name indicates, LVEM operates at low voltage electron beam (usually below 5 kV).
  • This lower energy minimizes heat generation and damage to sensitive samples and enhances contrast for biological samples.
  • It is used to observe unstained samples of biological tissues, polymers, and other soft materials.
  • It resolves up to 1-2 nanometers and eliminates the need for sample preparation requirements.

Unlike other microscopes, the maintenance and operation of an electron microscope can be costly.

It needs a separate housing and a nitrogen plant for use during operation as it generates a large amount of heat.

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