On average, there are 100,000 hairs on a human head. Everyone is born with a set amount of hair follicles. Hair grows from follicles that enclose the hair root in the person's scalp. The reason children's hair looks thicker is because their heads are smaller.
Hair is made out of keratin as are nails, hooves, scales and feathers. It grows in three phases: telogen, anagen and catagen. The hair grows about a centimeter every month during the anagen phase. It shrinks during the catagen phase, where it forms a club hair that clings to the hair root. In the telogen phase, the hair rests.