* Hair: Primarily composed of keratin, a fibrous structural protein. Hair grows from follicles embedded in the skin (dermis). The visible part of the hair, the hair shaft, is made of dead cells. Growth occurs at the base of the follicle, pushing older cells outward.
* Nails: Also composed of keratin, but a different type of keratin that is harder and more densely packed than that found in hair. Nails grow from the nail matrix located under the proximal nail fold (cuticle). Like hair, the visible part of the nail (nail plate) is made of dead cells. Growth occurs at the matrix, with new cells pushing older cells forward.
In summary:
* Both hair and nails are primarily made of keratin.
* Hair grows from follicles, while nails grow from the nail matrix.
* Nail keratin is harder and more densely packed than hair keratin.