Background: Melasma is a frequent chronic acquired focal hypermelanosis that affects photoexposed areas in adults, especially women of reproductive age. While skin pigmentation from sun tanning and postinflammatory hyperpigmentation fades spontaneously after the stimulus cessation; in melasma, this reduction usually does not occur. Melasma evolves from alterations in several skin layers and cell types to hyperfunctional melanocytes, which produce and transfer mature melanosomes to the whole epidermis. Histopathological changes in the dermis, including basement membrane disruption, pendulous melanocytes, melanophages, mast cells, stem cell factor and c-KIT receptor, solar elastosis, and neovascularization, may play a role in the pathogenesis of melasma. These findings could serve as potential target treatments since this condition is often recalcitrant and requires a multimodal approach. The diagnosis of melasma is usually made clinically due to its characteristic appearance. In addition to the clinical classification based upon distribution pattern , melasma has also been subdivided into four subtypes based on different depths of melanin pigment. The use of additional tools such as Wood’s lamp, dermoscopy, and reflectance confocal microscopy (RCM) can help in the classification of melasma into epidermal, dermal, mixed, and indeterminate subtype. These classifications aid in prognosis and prediction of the therapeutic outcome. The MASI and mMASI are still the gold-standard in melasma scoring systems and should be used routinely in all therapeutic trials for melasma. The automated mMASI (aMASI) system via computer image analysis holds much promise but remains to be validated for consistency and applicability on worldwide basis.