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A microscope is an instrument used to see objects that are too small 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 many types of microscopes, the most common and first to be invented is the optical microscope which uses light to image the sample. Other major types of microscopes are the electron microscope (both the transmission electron microscope and the scanning electron microscope) and the various types of scanning probe microscope.
The first microscope to be developed was the optical microscope, although the original inventor is not easy to identify. An early microscope was made in 1590 in Middelburg, Netherlands.Two eyeglass makers are variously given credit: Hans Lippershey (who developed an early telescope) and Zacharias Janssen. Giovanni Faber coined the name microscope for Galileo Galilei's compound microscope in 1625 (Galileo had called it the "occhiolino" or "little eye").
Rise of modern light microscopy
The first detailed account of the interior construction of living tissue based on the use of a microscope did not appear until 1644, in Giambattista Odierna's L'occhio della mosca, or The Fly's Eye.
It was not until the 1660s and 1670s that the microscope was used extensively for research in Italy, The Netherlands and England. Marcelo Malpighi in Italy began the analysis of biological structures beginning with the lungs. Robert Hooke's Micrographia had a huge impact, largely because of its impressive illustrations. The greatest contribution came from Antonie van Leeuwenhoek who discovered red blood cells and spermatozoa and helped popularise microscopy as a technique. On 9 October 1676, Van Leeuwenhoek reported the discovery of micro-organisms.
In 1893 August Köhler developed a key technique for sample illumination, Köhler illumination, which is central to modern light microscopy. This method of sample illumination gives rise to extremely even lighting and overcomes many limitations of older techniques of sample illumination. Further developments in sample illumination came from Fritz Zernike in 1953 and George Nomarski 1955 for their development of phase contrast and differential interference contrast illumination which allow imaging of transpaElectron microscopy.
In the early 1900s a significant alternative to light microscopy was developed, using electrons rather than light to generate the image. Ernst Ruska started development of the first electron microscope in 1931 which was the transmission electron microscope (TEM). The transmission electron microscope works on the same principle as an optical microscope but uses electrons in the place of light and electromagnets in the place of glass lenses. Use of electrons instead of light allows a much higher resolution.
Development of the transmission electron microscope was quickly followed in 1935 by the development of the scanning electron microscope by Max Knoll.
Electron microscopes quickly became popular following the Second World War. Ernst Ruska, working at Siemens developed the first commercial transmission electron microscope and major scientific conferences on electron microscopy started being held in the 1950s. In 1965 the first commercial scanning electron microscope was developed by Professor Sir Charles Oatley and his postgraduate student Gary Stewart and marketed by the Cambridge Instrument Company as the "Stereoscan".
Scanning probe microscopy
The 1980s saw the development of the first scanning probe microscopes. The first was the scanning tunneling microscope in 1981, developed by Gerd Binnig and Heinrich Rohrer. This was closely followed in 1986 with Gerd Binnig, Quate, and Gerber's invention of the atomic force microscope.
Fluorescence and light microscopy
See also: fluorescence microscope, immunofluorescence, and confocal microscope
The most recent developments in light microscope largely centre on the rise of fluorescence microscopy in biology. During the last decades of the 20th century, particularly in the post-genomic era, many techniques for fluorescent labeling of cellular structures were developed. The main groups of techniques are small chemical staining of cellular structures, for example DAPI to label DNA, use of antibodies conjugated to fluorescent reporters, see immunofluorescence, and fluorescent proteins, such as green fluorescent protein. These techniques use these different fluorophores for analysis of cell structure at a molecular level in both live and fixed samples.
The rise of fluorescence microscopy drove the development of a major modern microscope design, the confocal microscope. The principle was patented in 1957 by Marvin Minsky, although laser technology limited practical application of the technique. It was not until 1978 when Thomas and Christoph Cremer developed the first practical confocal laser scanning microscope and the technique rapidly gained popularity through the 1980s.
Much current research (in the early 21st century) on optical microscope techniques is focused on development of superresolution analysis of fluorescently labeled samples. Structured illumination can improve resolution by around two to four times and techniques like stimulated Emission Depletion microscopy are approaching the resolution of electron microscopes.
Types of microscopes
• Light microscope:
Light microscope is a common optical device using the visible wavelengths. Optical microscopes are widely used for viewing small objects in colour. It can be binocular and monocular, trinocular for the use of video capturing devices.These microscopes use refractive lenses and eyepieces made of glass to direct a magnified image to the eye or other capturing device. The usual Light microscope magnification is 1500x but could also reach 2000x with less viewing quality.
• Compound microscope:
Compound microscope is the most practiced microscope in science, work and hobby. It consists of two optical parts: ocular lens (the one next to your eyes) and the objective lens (the one positioned close to the watched sample). Compound microscope was first introduced by the Dutch spectacle maker Zacharias Janssen (he is also known for inventing a telescope). His sophisticated device for a year 1590 performed two tasks: viewing stars and small objects. The instrument became the invention of the first compound microscope and telescope at the same time.
• Digital microscope : USB microscope:
Digital microscope. A microscope, a video capturing device and a video screen forming one unit without eye pieces is a proper definition of a digital microscope. On the other hand, if you mount a digital camera on a trinocular microscope for example, it would also make a good "unofficial" digital microscope or USB microscope. For a better image or video resolution and overall quality, it is better using a proper digital microscope as the digital microscope lens is made specifically for the camera. The most common digital microscope has a 15 inch monitor and around 2 million pixel camera.
• Fluorescence microscope:
A fluorescence microscope is an equal to common light microscopes instrument with the exception that it illuminates specimen with the light of a special wavelength causing the observed object to emit light with a different colour due to absorbtion by the fluorophores. Life sciences widely use fluorescence microscopes, mostly the type called "epifluorescence microscopes". Fluorescence microscopes are very useful in all fields of biology, making it possible to study more thoroughly protein and other molecules.
• Electron microscope : scanning:
Electron microscope is one of the most sophisticated microscopes known in science. Electron microscope uses electrostatic and electromagnetic lenses and by means of electrons illuminating an object, magnifying an image up to 2 million times while light microscopes only 2 thousand times. Electron microscope uses a wavelength of an electron called Broglie wavelength. By controlling the beam of electromagnetic radiation electron microscope makes it possible to focus it, producing an image of the greatest scale.
• Stereo microscope:
The stereo microscope or "dissecting microscope" is an optical microscope used for detailed three dimentional vision. Catching the light with two objectives, stereo microscope allows better studies of thick specimen. Capable of dark field observations stereo microscope functions by means of two separate light beams making the visual stereo effect. Stereo microscopes are not very powerful though, their useful magnification is not greater than 100 and 10 times in the average use. Some stereo microscopes use auxiliary objectives for more magnification.
• Microscope camera:
• Microscope video recording has become one of the common procedures in microscopy. Microscope camera can be build into a digital microscope or mounted on a trinocular microscope. Microscope camera is a special video capturing device designed for microscopes which can not be used for other purposes. Most of conventional digital cameras can be used for filming microscope images by means of adapters. Under-microscope.com uses a special microscope digital camera DCM500 for video and image taking with a considerably high resolution of 5million pixels.
Timeline of the Microscope
• 14th century: Spectacles first made in Italy • 1590: Two Dutch spectacle-makers and father-and-son team, Hans and Zacharias Janssen, create the first microscope. • 1667: Robert Hooke's famous "Micrographia" is published, which outlines Hooke's various studies using the microscope. • 1675: Enter Anton van Leeuwenhoek, who used a microscope with one lens to observe insects and other specimen. Leeuwenhoek was the first to observe bacteria. • 18th century: As technology improved, microscopy became more popular among scientists. Part of this was due to the discovery that combining two types of glass reduced the chromatic effect. • 1830: Joseph Jackson Lister discovers that using weak lenses together at various distances provided clear magnification. • 1878: A mathematical theory linking resolution to light wavelength is invented by Ernst Abbe. • 1903: Richard Zsigmondy invents the ultramicroscope, which allows for observation of specimens below the wavelength of light. • 1932: Transparent biological materials are studied for the first time using Frits Xernike's invention of the phase-contrast microscope. • 1938: Just six years after the invention of the phase contrast microscope comes the electron microscope, developed by Ernst Ruska, who realized that using electrons in microscopy enhanced resolution. • 1981: 3-D specimen images possible with the invention of the scanning tunneling microscope by Gerd Binnig and Heinrich Rohrer.
