We are all born with about 100,000 hair follicles which start as single follicles. On the average human head there is approximately 2,200 strands of hair per square inch. As you age, the single follicles then double and triple creating the hair's thickness and fullness. Over time the follicle reverses back to single a follicle. The thickness changes and the amount of hair growth decreases. Hair thickness directly correlates to the size of the hair follicles which varies for each individual. On average the thickness of each strand is about .10 millimeters. The growth cycle never stops it changes depending on what the body is experiencing.
THE ANAGEN PHASE
Longevity: Three to five years
Details: The first phase of the hair growth cycle, this is when the hair physically grows out from the follicle. A hair can grow up to 30 inches in the anagen phase.
THE CATAGEN PHASE
Longevity: 10 days
Details: This second phase is phase is actually a transitional period where the hair stops growing as it prepares to falls out shortly.
THE TELOGEN PHASE
Longevity: Three months
Details: The final part of the growth cycle, this is when the hair falls out from the follicle and rests before the growth cycle begins again.