Ellipsoid and spheroid melanosomes similar to those found in the hair matrix melanocytes of eumelanic C57BL mice and pheomelanic Ay mice, respectively, have been shown to coexist in the same human melanocyte. The difference in the three-dimensional ultrastructure of these melanosomes of the human hair matrix melanocyte has been determined by high-voltage transmission electron microscopy using a goni ometer. By energy-dispersive X-ray spectroscopy, sulfur, one of the main characteristic chemical properties of pheo-