The science of investigating small objects using an optical instrument is called microscopy. Microscopic means invisible to the eye unless aided by a microscope.
The human eye has a resolution in the order of 100 µm (10-4 m), which is about the thickness of a hair. With the microscope, whole worlds become available, filled with knowledge that can serve as inspiration. The exploration of the micro-cosmos has led to numerous discoveries, without which we would be left with the limited knowledge our eyes give us.
Long into the distant unrecorded past, someone picked up a piece of transparent crystal thicker in the middle than at the edges, looked through it, and discovered that it made things look larger. Someone also found that such a crystal would focus the sun's rays and set fire to a piece of parchment or cloth. Magnifiers and "burning glasses" or "magnifying glasses" are mentioned in the writings of Seneca and Pliny the Elder, Roman philosophers during the first century A. D., but apparently they were not used much until the invention of spectacles, toward the end of the 13th century. They were named lenses because they are shaped like the seeds of a lentil.
An early microscope was first recorded as being made in 1590 in Middelburg, Netherlands. Two eyeglass makers are variously given credit: Hans Lippershey (who developed an early telescope) and Zacharias Janssen. This simple microscope was a tube with a plate for the object at one end and, at the other, a lens which gave a magnification less than ten diameters -- ten times the actual size. These excited general wonder when used to view fleas or other tiny insects and so were sometimes dubbed as "flea glasses." The development of this conventional microscope at the end of the 16th century led to a great step forward for science, particularly in biology and medicine. In the beginning though, the microscope was mainly a toy in rich homes.
Giovanni Faber coined the name microscope for Galileo Galilei's compound microscope in 1625 (Galileo had called it the "occhiolino" or "little eye"). But many important discoveries followed. 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. Scientists have also discovered and explored life's own building block - the cell. This great contribution came from Antonie van Leeuwenhoek who discovered red blood cells and spermatozoa and helped popularise microscopy as a technique. This first scientific result based on microscopy dealt with the circulatory blood system and changed our view of the human body. Different types of bacteria and the following struggle against diseases, as well as studies of different materials and their qualities are other valuable results. 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. At the end of the nineteenth century the physical limits in the form of the wavelength of light stopped the quest to see further into the micro-cosmos. This method of simple illumination had many limitations. Further developments in 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 transparent samples.
With the theories of quantum physics, new possibilities appeared - the electron with its extremely short wavelength could be used as "light-source" in microscopes with unprecedented resolution. The first prototype of the electron microscope was constructed around 1930. In the following decades, smaller and smaller things could be studied. Viruses were identified and with magnifications up to one million, even atoms finally became visible.
Since photography has developed hand in hand with different techniques of microscopy, the public has been able to follow close in the footsteps of scientists. Pictures of cell division, nerves that make up the brain and single atoms have changed our view of the human body and nature itself. Even today our ability to lurk into nature increases further, owing to new techniques of microscopy for studying delicate processes within the cell or the building of materials atom by atom with nanotechnology.