Invention The earliest microscopes were single
lens magnifying glasses with limited magnification, which date at least as far back as the widespread use of lenses in
eyeglasses in the 13th century. Compound microscopes first appeared in Europe around 1620 The actual inventor of the compound microscope is unknown although many claims have been made over the years. These include a claim 35 years after they appeared by
Dutch spectacle-maker Johannes Zachariassen that his father,
Zacharias Janssen, invented the compound microscope and/or the telescope as early as 1590. Johannes' testimony, which some claim is dubious, pushes the invention date so far back that Zacharias would have been a child at the time, leading to speculation that, for Johannes' claim to be true, the compound microscope would have to have been invented by Johannes' grandfather, Hans Martens. Other historians point to the Dutch innovator Cornelis Drebbel with his 1621 compound microscope. and/or could look through the wrong end in reverse to magnify small objects. The only drawback was that his 2 foot long telescope had to be extended out to 6 feet to view objects that close. After seeing the compound microscope built by Drebbel exhibited in Rome in 1624, Galileo built his own improved version. (Galileo had called it the "
occhiolino" or "
little eye"). Faber coined the name from the
Greek words
μικρόν (micron) meaning "small", and
σκοπεῖν (skopein) meaning "to look at", a name meant to be analogous with "telescope", another word coined by the Linceans.
Christiaan Huygens, another Dutchman, developed a simple 2-lens ocular system in the late 17th century that was
achromatically corrected, and therefore a huge step forward in microscope development. The Huygens ocular is still being produced to this day, but suffers from a small field size, and other minor disadvantages.
Popularization , 1630
Antonie van Leeuwenhoek (1632–1724) is credited with bringing the microscope to the attention of biologists, even though simple magnifying lenses were already being produced in the 16th century. Van Leeuwenhoek's home-made microscopes were simple microscopes, with a single very small, yet strong lens. They were awkward in use, but enabled van Leeuwenhoek to see detailed images. It took about 150 years of optical development before the compound microscope was able to provide the same quality image as van Leeuwenhoek's simple microscopes, due to difficulties in configuring multiple lenses. In the 1850s,
John Leonard Riddell, Professor of Chemistry at
Tulane University, invented the first practical binocular microscope while carrying out one of the earliest and most extensive American microscopic investigations of
cholera.
Lighting techniques While basic microscope technology and optics have been available for over 400 years it is much more recently that techniques in sample illumination were developed to generate the high quality images seen today. In August 1893,
August Köhler developed
Köhler illumination. This method of sample illumination gives rise to extremely even lighting and overcomes many limitations of older techniques of sample illumination. Before development of Köhler illumination the image of the light source, for example a
lightbulb filament, was always visible in the image of the sample. The
Nobel Prize in physics was awarded to Dutch physicist
Frits Zernike in 1953 for his development of
phase contrast illumination which allows imaging of transparent samples. By using
interference rather than
absorption of light, extremely transparent samples, such as live
mammalian cells, can be imaged without having to use staining techniques. Just two years later, in 1955,
Georges Nomarski published the theory for
differential interference contrast microscopy, another
interference-based imaging technique.
Fluorescence microscopy Modern biological microscopy depends heavily on the development of
fluorescent probes for specific structures within a cell. In contrast to normal transilluminated light microscopy, in
fluorescence microscopy the sample is illuminated through the objective lens with a narrow set of wavelengths of light. This light interacts with fluorophores in the sample which then emit light of a longer
wavelength. It is this emitted light which makes up the image. Since the mid-20th century chemical fluorescent stains, such as
DAPI which binds to
DNA, have been used to label specific structures within the cell. More recent developments include
immunofluorescence, which uses fluorescently labelled
antibodies to recognise specific proteins within a sample, and fluorescent proteins like
GFP which a live cell can
express making it fluorescent. ==Components==