Pigment cells are easily distinguished as they contain brown pigment (melanin) in their cytoplasm. They are most abundant in connective tissue of the skin, and in the choroid and iris of the eyeball.

Along with pigment containing epithelial cells they give the skin, the iris, and the choroid their dark colour . Variations in the number of pigment cells, and in the amount of pigment in them accounts for differences in skin colour of different races, and in different individuals. Of the many cells that contain pigment in their cytoplasm only a few are actually capable of synthesising melanin. Such cells, called melanocytes, are of neural crest origin.

The remaining cells are those that have engulfed pigment released by other cells. Typically, such cells are star shaped (stellate) with long branching processes. In contrast to melanocytes such cells are called chromatophores or melanophores. They are probably modified fibroblasts.

Pigment cells prevent light from reaching other cells. The importance of this function in relation to the eyeball is obvious. Pigment cells in the skin protect deeper tissues from the effects of light (specially ultraviolet light). The darker skin of races living in tropical climates is an obvious adaptation for this purpose.