Melanin

Melanin denotes a family of biological pigments formed through oxidative chemistry of aromatic precursors. It is not one small molecule with a single universally applicable molecular formula. Different precursor chemistry and assembly give chemically heterogeneous materials.

Dark eumelanin and sulfur-containing pheomelanin illustrate the family's diversity. Extended electronic interactions and structural disorder produce broad absorption rather than one isolated sharp molecular line. Consequently colour, composition and microscopic organization must be considered together when comparing melanin specimens; assigning a precise repeating structure to every biological sample is generally too strong.