Scanning electron microscopy (SEM) is used to examine the structure of natu
ral and synthetic melanins. Eumelanin from Sepia officinalis and synthetic
eumelanin are found to be structurally dissimilar. The natural sample has a
significant structural order with subunits that have a lateral dimension o
f similar to 15 nm. The synthetic samples, on the other hand, appear to be
amorphous solids. These results lend support for the existence of fundament
al structural units proposed from the analyses of wide-angle X-ray diffract
ion measurements and previous mass-spectrometry results. These findings als
o provide insight into the disparate photophysical behavior of Sepia and sy
nthetic eumelanin.