Although ray and wave optics are capable of explaining most of the day-to-day observations, they are incapable of explaining many important effects of light. These effects, although on small scales give rise to a noticeable outcomes. Some of the examples include, electric effects of light on certain metal surfaces (plasmonics), and light passing through birefringent materials and specific crystals (such as, Quartz). In addition, light gets altered by magnetic fields causing it to rotate when it passes through certain media in the presence of a magnetic field (Faraday effect). These and many other examples prompt us to believe that light does have non-zero electric and magnetic effects. So, light can be further sub-classified as magnetic and electric field vector waves also known as electromagnetic waves. Concentrated electromagnetic fields are an essential feature of optical microscopy and high NA objective lenses are used to tightly focus electric fields. The theory allows computation of electric field at the focus which forms the basis to understand all kinds of microscopy systems (epifluorescence, confocal and two-photon microscopy). In addition, field-dipole interaction is the foundation for all kinds of polarization microscopy. This gives the essence of the electromagnetic nature of light in optical microscopy.