Final answer:
Keratinocytes are the main type of cells found in the epidermis, producing the protein keratin.
Step-by-step explanation:
Keratinocytes are the main type of cells found in the epidermis, the outer layer of the skin. They produce a tough protein called keratin, which gives the skin its hardness and water-resistant properties. Keratinocytes are constantly dividing in the lower layers of the epidermis and as they move towards the surface, they fill with keratin and eventually die, forming the protective layer of dead skin cells called the stratum corneum.