Hairs are made up of keratin which  is a special protein resistant to wear and tear. It is the protein that also makes up the nails.

The diameter of a single hair fiber varies from person to person; but it is usually around 0.05 to 0.09 millimeters.

Each hair arises from a hair follicle. The hair follicle is the point from which the hair grows. It is a dint buried in the fat of the scalp which is  indentation in the outermost and deeper layers of skin called the epidermis and dermis. This is made up of various structures:

Hair Bulb

The terminal part of the hair follicle seated within the skin which is the living part of the hair. Cells here divide every 24-72 hours and produce the long and  cylindrical shaped hair fibers. Here in the hair bulb, there are some special cells called melanocytes, which produce the pigment called melanin  that gives the hair its color. We also know that receptors for the male hormones - androgens, are located on the cells of this structure.

Dermal Papilla: At the base of each hair bulb is the dermal papilla containing the blood supply to the follicle. Thus, it is essential for the nourishment of the growing hairs.

Sheaths: Within the skin, internal and external root sheaths cover the hair follicles and protect it.

Sebaceous Gland: This is a gland that h produces and secretes the natural oils called srbum lubricating hairs.

Erector pillae muscles: A small muscle that causes the hair to stand on end

Hair Shaft

The part of the hair seen above the skin is called the hair shaft. The hair shaft is made up of dead cells that have turned into keratin and binding material, together with small amounts of water. This structure explains why we do not feel any pain while our hair is being cut.