Keratin is a tough, fibrous protein that is a key structural component in many parts of the body. It is found in hair, nails, and the outer layer of skin, providing strength and protection. This protein helps to create a barrier against environmental damage, making it essential for maintaining healthy skin and hair. In addition to its role in humans, keratin is also present in the feathers of birds, the hooves of horses, and the shells of tortoises. Its unique properties make it a popular ingredient in beauty products, such as shampoos and conditioners, aimed at improving the health and appearance of hair.