The outermost and nonvascular layer of the skin, derived from the embryonic ectoderm, varying in thickness from 0.07–1.4 mm. It comprises, from within outward, five layers: (1) basal layer (stratum basale), ; (2) prickle cell or spinous layer (stratum spinosum), (3) granular layer (stratum granulosum), (4) clear layer (stratum lucidum), and (5) horny layer (stratum corneum).