The periderm is a transient, single-layer squamous epithelium that serves as an outer protective layer during embryogenesis. This epithelium is always the most superficial layer under which all the layers of the epidermis are formed following terminal epidermal differentiation. Few studies have investigated the periderm. My research aims to do a systematic analysis of the periderm to define this epidermal layer across embryonic development. I study mouse embryos deficient for Interferon Regulatory Factor 6 (Irf6), a gene involved in epidermal differentiation and proliferation, as my experimental model due to their phenotypic lack of terminal epidermal differentiation. I utilize biochemical and microscopy techniques to accomplish this study.