Introduction

We know that our body is made up of cells. All animals and plants are made up of cells. In 1665 Robert Hooke, an English scientist observed a section of cork under a crude microscope. He found a network or honey comb like structure with small compartments. He felt these closed compartments similar to closed rooms that are a cell and this is how cells were first reported. Today cell is a living structure. A cell is active unit. It has very large number chemicals and actively participates in growth, metabolism and every activity. Most cells are microscopic. Cells also have various shapes and sizes. Cells also perform a variety of functions. Study of cells is called cytology or Cell biology. Study of cells and their structures has been greatly eased because of Microscopes.

 

Microscopy

A microscope (from the Greek: mikr´os, ”small” and skopeˆın, ”to look” or ”see”) is an instrument to see objects too tiny for the naked eye. The science of investigating small objects using such an instrument is called microscopy. Microscopic means invisible to the eye unless aided by a microscope

There are various types of microscopes. Some of them are:

• Simple microscope: Light microscope consisting of a single convex lens that is used to produce an enlarged image; ”the magnifying glass was invented by Roger Bacon in 1250”

• Compound microscope: Optical microscopes, using visible wavelengths of light, are the simplest and most used. Optical microscopes have refractive glass and occasionally of plastic or quartz, to focus light into the eye or another light detector. Mirror-based optical microscopes operate in the same manner. Typical magnification of a light microscope, assuming visible range light, is up to 1500x with a theoretical resolution limit of around 0.2 micrometers or 200 nanometers
• Phase contrast microscope: The phase contrast microscope is widely used for examining such specimens as biological tissues. It is a type of light microscopy that enhances contrasts of transparent and colorless objects by influencing the optical path of light. The phase contrast microscope is able to show components in a cell or bacteria, which would be very difficult to see in an ordinary light microscope.

 

Electron microscope

A magnification of two billion times is possible by electron microscope. Three major types of electron microscopes exist :

• Scanning electron microscope (SEM): It looks at the surface of bulk objects by scanning the surface with a fine electron beam and measuring reflection.
• Transmission electron microscope (TEM): It passes electrons completely through the sample .This is a scientific device that allows people to see objects that could normally not be seen by the naked or unaided eye.
• Scanning Tunneling Microscope (STM): Is a powerful technique for viewing surfaces at the atomic level.