In hair follicles, melanocytes originate from melanocyte stem cells (McSCs). They directly adhere to hair follicle stem cells (the niche cells for McSCs) and reside in the hair follicle bulge-subbulge area, serving as a melanocyte reservoir for skin and hair pigmentation. McSCs form a stem cell system within the individual hair follicle and provide a "hair pigmentary unit" for each cycle of hair pigmentation. Melanocyte stem cells in hair follicles undergo cyclic activation, degeneration, and resting phases to pigment hair and preserve the stem cells. The quiescence, maintenance, activation, and proliferation of McSCs are controlled by specific activities in the niche, influencing the differentiation and regeneration of melanocytes. Therefore, the research on McSCs and niche would contribute to the application of McSCs in treating various skin pigmentary disorders.