The mid-follicle region
In this part of the follicle the actively growing cells die and harden into what we call a hair. As the cells below continue to divide and push upwards, the hair grows upwards too, out of the skin. It now consists of a mixture of different forms of the special hair protein, keratin.
  Some of these keratins contain a high level of sulphur, some much less. The sulphur plays an important part in the way the hair behaves, especially when it is given cosmetic treatments. You will find more about this later in the book.

The hair shaft

This is the part of the hair that can be seen above the scalp. It consists mainly of dead cells that have turned into keratins and binding material, together with small amounts of water.
  Terminal hairs on the head are lubricated by a natural oil (sebum) produced by the sebaceous glands of the follicles. How much natural oil your glands produce is mostly determined by your genetic inheritance. But in addition boys' and girls' glands tend to produce more oil when