The skin is one of the largest organs of the body, and it has multiple functions: metabolic, temperature regulator, sensibility, and protection. The skin is formed by three layers: epidermis, dermis and hypodermis; the annexed ones are found in the dermis: hair follicles, sebaceous glands, sweat glands; the nails are found in the appendix. Although the skin structure in domestic animals is similar, there are variations among species and even in a single specie related to epidermal thickness, dermal thickness, types and arrangements of hair follicles, and annexed structures. Knowing that Skin’s diseases are common in clinic practices in small animals, this article will review the normal histology structure of dog’s skin in order to know the changes in skin’s diseases in this specie.