Abstract: The three-dimensional achitecture of the collagen fibrous network in infants, adults and aged persons was studied by scanning electron microscopy. The medial side of upper arm, abdomen and the heel were the sites of examination. The results showed that the collagen fibers of the infant were fine and arranged mainly parallel to the skin surface, there was no clear border between papillary and reticular dermis. The features of different sites were similar. The fibers of the adult were coarser and the orientation of the fibers was totally random. There was a clear distinction between papillary and reticular dermis and a "mid zone" separating them. The network of the heel was denser than that of other sites. The organization of the network of the aged was even more dense and random. The fibers were straighter and less tightly interwoven. Unravelling of fiber bundles was found. The bundles of the heel were very closely packed. The reasons of the structural difference of the fibrous network and their relation with the biological properties are discussed.