Which type of epithelial cells makes up the outermost layer of skin?

The outermost layer of the skin is composed of stratified squamous epithelial cells. This type of epithelium consists of multiple layers of flattened cells that are organized in a stratified manner. The exact number of layers depends on the specific location of the epithelium within the body. The skin over most parts of the body has 4 layers of skin, while the palms of the hands and soles of the feet have 5 layers. 

Stratified squamous epithelium is primarily protective in function, guarding against the invasion of foreign microorganisms into underlying tissues. The outermost layer of the epithelium is composed of fully keratinized and dead cells that act as a barrier against external environmental factors, pathogens, and water loss. This intricate structure of stratified squamous epithelium is crucial for the skin's function as a protective barrier for the underlying tissues and body.