A. Electron micrograph of a keratinized layer of an opossum baby 0 day after birth: Many keratohyaline granules are included in the cells (arrow). Scale bar 1 µm. B. Electron micrograph of an epidermis and a dermis of a baby 0 day after birth: border between the epidermis and the dermis is clear, and two types of fibroblasts are observed within the dermis. OF; oval or polygonal fibroblast, SF; slim fibroblast. Scale bar 10 µm. C. Electron micrograph of a fibroblast and the neighboring intercellular space from a baby 0 day after birth. The fibroblast contains compact packed endoplasmic reticula in its cytoplasm. Bundles of Collagen fibers are observed at the space. Scale bar 1 µm. D. Enlarged view of the bundle which marked in Fig. 1C. The bundle is composed of some collagen fibers. Scale bar 0.25 µm.