Keratinization is the process by which skin cells produce a tough protein called keratin. This protein helps form a protective barrier on the skin's surface, making it resilient against environmental damage, pathogens, and water loss. As cells move from the deeper layers of the skin to the surface, they gradually fill with keratin and eventually die, forming a layer of dead cells. This process is essential for maintaining healthy skin and is also observed in other areas of the body, such as hair and nails. Keratinization helps these structures remain strong and durable, contributing to overall body protection and function.