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Types of Microscopes: Electron, Light & Fluorescence Video

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  • 0:00 What Is a Microscope?
  • 0:44 Light Microscopes
  • 2:21 Fluorescence Microscopes
  • 3:06 Electron Microscopes
  • 4:32 Lesson Summary
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Lesson Transcript
Instructor: Betsy Chesnutt

Betsy teaches college physics, biology, and engineering and has a Ph.D. in Biomedical Engineering

Microscopes are used to visualize tiny objects and structures that cannot be seen with the naked eye. In this lesson, learn how light, fluorescence, and electron microscopes work and how they are used in scientific and medical research.

What Is a Microscope?

Have you ever wondered what tiny creatures might be living in a puddle of water? Well, want to know more? Because you are looking at some in this image right now!

green algae under microscope

Many years ago, scientists wanted to know this too, and so they used lenses to magnify a drop of water, allowing us to see the world of single celled organisms for the very first time! These early microscopes used a light source and one or more optical lenses to magnify an object. Today, we still use light microscopes to see objects that are too small to see with the naked eye, but we also use other types of microscopes, like electron microscopes and fluorescence microscopes, to see things that you can't see even with a light microscope!

Light Microscopes

Microscopes that use light and optical lenses to magnify tiny objects are called light microscopes or optical microscopes. Light microscopes have been used for more than 400 years and are still the most common type of microscope in use today. In the 1600's, the Dutch biologist Antonie van Leeuwenhoek developed a simple optical microscope, which only had one lens and used the sun as a light source. Compound microscopes, light microscopes with more than one lens, had been invented in the 1500s, but could only magnify up to 40x. Leeuwenhoek's magnified over 200x. He became the first scientist to see tiny single-celled organisms living in water, on his own teeth, in the blood stream, and anywhere else he could think of. He called what he found 'animalcules,' but we now know them to be protozoa, bacteria, blood cells, sperm cells, and the list goes on.

Later, compound microscopes became more sophisticated and can now magnify objects much more than simple microscopes. Almost all light microscopes used today are compound microscopes. Most modern compound light microscopes have the same basic components. The first is an eyepiece containing an ocular lens. This is the part of the microscope that you look into, and it provides some magnification of the object you are looking at (typical magnifications range from 2x to 50x). They also have an objective lens that is placed just above the object you want to magnify and magnifies the object even more. A light source illuminates the object and a movable stage holds the sample and can be moved up and down using focusing knobs to bring the image into focus.

Fluorescence Microscopes

A specialized type of optical microscope, called a fluorescence microscope, uses fluorescence to create an image. In a fluorescence microscope, specimens are first stained with a fluorescent dye that binds specifically to certain compounds in the specimen. Then, light of a single wavelength is used to cause the fluorescent dyes to give off light that can be picked up by a detector. Fluorescent microscopes are very useful in the life sciences where they are used to visualize the expression of specific proteins or other molecules inside cells. Check out this image:

fluorescent cells

In this endothelial cell, fluorescence microscopy shows nuclei which are stained blue, microtubules which are stained green, and actin filaments which are stained red.

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