Hair is a protein filament that grows from follicles found in the dermis, or skin. It is primarily made of a protein called keratin, which is also found in nails and the outer layer of skin. Hair serves various functions, including protection, regulation of body temperature, and facilitation of the sense of touch. In humans, hair can vary in color, texture, and density, influenced by genetics and environmental factors. Hair growth occurs in cycles, with each strand going through phases of growth, rest, and shedding. Proper care and maintenance can enhance hair health and appearance, making it an important aspect of personal grooming.