20th Century
At the turn of the 19th/20th centuries Louis Pasteur invented pasteurization while Robert Koch discovered his famous or infamous postulates: the anthrax bacillus, the tuberculosis bacillus and the cholera vibrio.
Phase Contrast MicroscopeUV and Phase: By 1900, the theoretic limit of resolution for visible light microscopes (2000 angstroms) had been reached. In 1904, Zeiss overcame this limitation with the introduction the first commercial UV microscope with resolution twice that of a visible light microscope. In 1930 Fritz Zernike discovered he could view unstained cells using the phase angle of rays. Spurned by Zeiss, his phase contrast innovation was not introduced until 1941 although he went on to win a Nobel Prize for his
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The subsequent interaction of the beam of electrons with the specimen is recorded and transformed into an image. Then, in 1942, Ruska improved on the TEM by building built the first scanning electron microscope (SEM) that transmits a beam of electrons across the specimen.
Ruska's principles still form the basis of modern electron microscopes - microscopes that can achieve magnification levels of up to 2 million times! The second major development for microscopes in the 20th century was the evolution of the mass market. Started in the 19th century when Leitz claimed to have exported 50,000 microscopes to the U.S., this trend accelerated in the 20th century. As a result, a large number of manufacturers sprang up to offer more competitively priced alternatives to established European companies such as Zeiss and Leitz.
China: China has become a major supplier of microscopes for everyday use and, with the evolution of their optical manufacturing capability, now supplies optical components to some of the major microscope brands. This market trend has had a beneficial effect on the price of microscopes, enabling the spread of microscopes beyond the realm of the research scientist to everyday commercial and individual