Mammalian hair follicles represent one of the most rapidly proliferating tissue systems in a living organism.  In humans, scalp hair typically grows at a rate of 1/2" per month, representing a remarkably robust rate of cell division.  Equally interesting, is the fact that hair goes through several distinct cycles, loosely analogous to the cycles deciduous tree leaves go through as the seasons change.  Like the leaves on a tree, hair follicles go through a growing stage (anagen) a shedding stage (catagen) and a resting stage (telogen).