The epidermis is composed of four main strata, or layers. The outermost layer is called the stratum corneum, which is Latin for ''horny layer.'' While we aren't literally covered in horny scales, this layer is tough nonetheless. It also varies in thickness depending on the body part it covers.he epidermis is made of four main layers, or strata 1  : The stratum corneum is the thick, tough outer layer. 2  It is made mostly of dead cells that slough off constantly. 3  The stratum basale is comprised of new cells that are constantly dividing to replace the stratum corneum.