Fig. 4. A skin equivalent consists minimally of a dermal equivalent and differentiated epidermis cultured first submerged then at the air-liquid interface in a three-dimensional context. Fibroblasts (arrows) encased in a type I collagen lattice provide dermal support for the epidermis. The epidermis is stratified and contains differentiated layers typically found in normal skin, including the (1) basal, (2) spinous, (3) granular and (4) cornified layers. Bar, 44 µm.