One of the foremost advancing techniques in the domain of scientific research is optical microscopy that enables imaging of cellular components and mechanisms. Modern light microscopy encompasses a variety of techniques, including brightfield, darkfield, and fluorescence microscopy, that have been especially designed to meet specific requirements of research. With the discovery of fluorescence imaging, subcellular and molecular components of live and fixed cells can be visualized with exceptional specificity and resolution. This chapter highlights the fundamentals of light microscopy and advancements in imaging methodologies such as fluorescence lifetime imaging microscopy (FLIM), widefield microscopy, confocal microscopy, and fluorescence resonance energy transfer (FRET), emphasizing its pivotal significance within modern science.