During the hair cycle, the middle and upper portions of the hair follicle are the permanent segments of the hair follicle, while the lower portion is non-permanent. The growing or anagen hairs are anchored deeply within the subcutaneous fat and cannot be pulled out easily. The telogen hairs are located higher up in the dermis and can be pulled out relatively easily. The scalp consists of almost 90% hairs in anagen, 1% in catagen and 10% in telogen. Anagen may last up to 2-6 years, telogen 3 months, and catagen 3 weeks. This ratio is usually uniformly distributed over the entire scalp. The dermal papilla (DP) is pulled upward with each cycle, and during telogen is closely associated with the stem cells of the bulge area. Communication signals between DP and stem cells of the bulge probably determine the length of anagen and the matrix girth of the next hair cycle.