Around the middle of the past millennium, there were many discoveries that one may describe as having changed the way we lived. Navigation using the compass opened up the world to colonists, gunpowder changed the way people waged wars, use of steam in machines changed the way we worked and moved around. But in the field of biology, the one discovery which completely changed the way we studied biology in general and the human body in particular has to be that of the microscope. Microscopes opened up a totally new world – that of structures too small to be seen by the human eye. And from the basic microscopes of the 16th and 17th centuries to the advanced electron and confocal microscopes of today, the journey has been nothing short of miraculous. But is it not surprising that the prime tool of biologists the world over was invented by a person who had absolutely nothing to do with the science? Let me take you through a brief history of the microscope, so as to better understand the evolution of these fantastic instruments.
A microscope is any instrument that enables you to see objects that are otherwise too small to be seen by the naked eye. A magnifying glass may well be the simplest microscope, and truly enough, in circa 1000 AD, a spherical piece of glass was laid over written material to magnify the text. As early as the first century AD, lenses (called so as they resemble lentil seeds) were used to focus sunlight on dry grass and start a fire. It was around the 13th century that eye glasses were invented, and lenses truly gained popularity by the 16th century.
In the Medieval World: The Pioneers
In 1590 AD, the Dutch father and son duo of Zacharias and Hans Janssen, eye-glass makers by profession, pieced together a contraption of a tube with multiple lenses placed in it, and discovered that one can see objects in a much larger size if viewed through their contraption. This is perhaps the first recorded instance of a microscope (and, probably a telescope too).
The discoverer of the cell, Robert Hooke also made his own version of the microscope, probably the first compound microscope, in 1655 AD. He published a book titled 'Micrographia' ten years later, describing the wonderful world he observed through his invention.
The person credited with having invented the microscope though, is Antonie van Leeuwenhoek. Leeuwenhoek was a trader by profession and an amateur lens grinder. It was he who invented the microscope as we know it today, replete with small glass lenses mounted in brass, and screws and pins to focus the sample under observation. Leeuwenhoek was a master in grinding lenses and created powerful lenses to the order of 270X-300X, that could magnify much more than what was ever possible earlier. His microscopes were instrumental in his discovery of blood cells, bacteria and sperms. Leeuwenhoek's microscope design was copied and/or improved upon by many including Robert Hooke.
In the Pre-Modern World
Subsequently, minor improvements in optics and design were made, but there was a general period of lull for the following two centuries. The next major milestone was Joseph Lister's effort in 1830 which lead to lenses having reduced chromatic effect. Lister showed that combining multiple weak lenses at specific distances reduced blurring and spherical aberration due to refraction of light. And thus was born the 'achromatic lens' as we know it today. Achromatic lenses could resolve up to 1 micron.
Making lenses and microscopes had now become a flourishing business, and Carl Zeiss in 1847 started making microscopes in the town of Jena in Germany. He was soon joined by Ernst Abbe, who authored a formula to calculate the maximum possible resolution in microscopes, known as the 'Abbe Sine Condition'. Abbe was also amongst the first to introduce the idea of lower magnification in the eyepiece, and more to the objective lens by his unique lens design techniques. New techniques in lens design led to the development of oil immersion lenses (1878), apochromatic (1886) and plan-apochromatic lenses. Otto Schott joined their firm in 1886 and brought with him expertise in optical glass properties, which led to Zeiss producing probably the best quality glass lenses in the world, which, in all probability, still holds today.
The adjacent image shows an 1879 Zeiss microscope.
It was soon established that using white light, one cannot resolve objects that are situated closer than half the wavelength of the light. As white light has a wavelength of 550 nm, no two objects situated 275 nm or lesser apart can be resolved. The solution was to use light of a shorter wavelength for illumination, and Richard Zsigmondy was the first to actually do it, creating the first ever Ultramicroscope. This achievement fetched him the Nobel Prize in Chemistry in 1925.
The next two Nobel Prize winning efforts for improved microscopes were for the Phase Contrast microscope and the Electron microscope, which were discovered in 1932 and 1931 respectively. The 1953 Nobel Prize in Physics was given to Frits Zernike, who invented the phase contrast microscope. Using phase contrast, one could study even colorless transparent objects.
The 1985 Nobel Prize in physics was awarded to Ernst Ruska, co-inventor of the electron microscope, which went a step ahead of the original ultramicroscope and used electrons as a source of light, enabling atomic-scale resolutions and magnification up to 1,000,000X.
Indeed, one can view in three dimensions, using the scanning electron microscope, sub-cellular ultra-structures in tremendous detail. The inventors of the scanning electron tunneling microscope, Gerd Binnig and Heinrich Rohrer were the recipients of the Nobel Prize for Physics in the subsequent year, 1986. The image beside shows a scanning electron micrograph of human red and white blood cells.
Modern microscopes like the laser scanning confocal microscope, scanning probe microscope and the atomic force microscope represent the pinnacle of microscopy made possible by vast advances in optics, technology and computing. These marvels are technologically superior to any other in the entire history of the microscope.
1. The History of the Microscope by Clay, R., Court, T., Holland Press, 1975.
2. Under the microscope: a brief history of microscopy by William J. Croft, World Scientific Publishing Co. Pte. Ltd., 2006
3. Image Credits:
- An 18th century Microscope by Daderot (Own work) [Public domain], via Wikimedia Commons
- circa 1751 Microscope by Roby
- circa 1780 Microscope by By Kierano (Own work) [GFDL or CC-BY-SA-3.0-2.5-2.0-1.0 (www.creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
- 1879 Zeiss Microscope by Dr. Timo Mappes, www.musoptin.com Mappes (Own work) [Public domain], via Wikimedia Commons
- SEM Red and White Blood Cells by Electron Microscopy Facility at The National Cancer Institute at Frederick (NCI-Frederick) () [Public domain], via Wikimedia Commons