Fluorescence microscopy is a type of light microscopy technique that is used to visualize and enlarge specimen that fluoresces. The process of fluorescence is caused by the presence of specific molecules that emit light of higher wavelength (emission) than the light absorbed by a specimen (excitation). As a result, the use of fluorochromes to stain specific cell or tissue components or bioorganic molecules enables the identification of the particular structures with a higher degree of specificity. As a result, the specimen has to be stained with fluorochromes (i.e., antibodies conjugated with a fluorescent label) or it must contain fluorescent molecule (i.e., recombinant fluorescent protein) to be visualized. As a result, only components that are specifically labeled or possess natural fluorescence can be detected by fluorescent microscopy.
Phase contrast microscopy is a type of light microscopy technique that improves contrast differences between the specimen (i.e., tissues, cell, organelles, etc.) and the surrounding medium. As a result, phase contrast microscopy provides the enlargement and visualization of the specimen components that do not absorb, refract or diffract light to be discriminated from the background. Due to the presence of a specific refractive index, cells and organelles bend some light that is passing through the specimen. Refracted and direct light rays are amplified by particular phase rings making the dark image on a light background. As a result, the specimen analysis does not require specific preparation, but the resolution is lower compared to fluorescent microscopy.