Taking an image with a fluorescent microscope and keeping it in its raw format might be sufficient for your needs. However, the appearance of such an image often benefits from image processing operations such as background subtraction, or more complex operations such as deconvolution or 3D rendering. You can even take this one step further and extract useful data from fluorescence microscopy images. This is called bioimage analysis and it allows you to quantify e.g. the intensities or sizes of objects, or to track structures in a time series.