#microscopy

A fluorescence microscope is an optical microscope that uses fluorescence and phosphorescence instead of, or in addition to, reflection and absorption to study properties of organic or inorganic substances.
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation while phosphorescence is a specific type of photoluminescence related to fluorescence.
Unlike fluorescence, a phosphorescent material does not immediately re-emit the radiation it absorbs.
The fluorescence microscope was devised in the early part of the twentieth century by August Köhler, Carl Reichert, and Heinrich Lehmann, among others.

Most cellular components are colorless and cannot be clearly distinguished under a microscope. The basic premise of fluorescence microscopy is to stain the components with dyes.
Fluorescent dyes, also known as fluorophores of fluorochromes, are molecules that absorb excitation light at a given wavelength (generally UV), and after a short delay emit light at a longer wavelength.The delay between absorption and emission is negligible, generally on the order of nanoseconds.
The emission light can then be filtered from the excitation light to reveal the location of the fluorophores.
Fluorescence microscopy uses a much higher intensity light to illuminate the sample. This light excites fluorescence species in the sample, which then emit light of a longer wavelength.
The image produced is based on the second light source or the emission wavelength of the fluorescent species — rathe rthan from the light originally used to illuminate, and excite, the sample.

Bright field microscopy:-
https://youtu.be/vRrwHOFyGzI

Dark field microscopy:-
https://youtu.be/J8z0IaxYXys

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