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 damage and preventing water loss. As cells move from the deeper layers of the skin to the surface, they gradually fill with keratin and eventually die, creating a layer of dead cells that protects the underlying tissues. This process is essential for maintaining healthy skin and is also found in other parts of the body, such as hair and nails. In areas of the body that experience more friction, like the palms and soles, keratinization is more pronounced, resulting in thicker skin.