Little is known about how the structures of connective tissue newly form during the wound-healing process. The authors investigated the repair process of excised skin wounds using alkali water cell maceration scanning electron microscopy. The development of the papillary dermis on the granulation surface proceeded toward the center of the wound, coupled with epidermis migration. No papillary dermis was evident on the granulation surface that had yet to be epithelialized. Finally, a layered structure as observed in normal dermis was reconstructed in the scar tissue. In other words, epidermis, basement membrane, and papillary dermis developed on the granulation surface accompanying epidermal migration, and reticular dermis as the result of maturation of granulation tissue. These findings demonstrate that both the papillary dermis and the reticular dermis develop differently after wounding, and that new papillary dermis and new epidermis develops as if completing “a unit” during the epithelialization process. The authors denote this unit the epithelialization unit.