A pigmented structure found in many animals, generally in the integument. The term is usually restricted to those structures that bring about changes in colour or brightness. A majority of chromatophores are single cells that are highly branched and contain pigment granules that can disperse or aggregate within the cell. However, in coleoid cephalopod mollusks (all mollusks except Nautilus), the chromatophores function as miniature organs, and changes in the dispersion of pigment are brought about by muscles. Although the mode of action of the two types of chromatophore is completely different, the effect is the same: pigment either is spread out over a large area of the body or is retracted into a small area.