Under normal circumstances hair growth in each hair follicle occurs in cycles. Cycling is a unique feature of the hair follicle, no other structure in an adult human or any mammal cycles in such a way. Foremost reason might be is that skin desquamation is an integral characteristic of all organisms. Hair being an appendage of the skin is also shed periodically. Hair follicle cycling also allows limiting the length of the hair shaft on a particular location in the body. The eye brows, facial hairs, scalp hair, etc. all have a distinct length as very long hairs on these parts would cause an impediment to seeing, smelling and other functions. The active growth phase in different skin locations differ, thereby restricting hair growth. Furthermore, the regular shedding of the shaft helps to clean the skin of any unwanted waste and other harmful toxic material that may be produced. It therefore serves as a survival mechanism. The regenerative property of the follicle also contributes to the survival mechanism. Whenever the follicle is destroyed, as in chemotherapy, the speed of cycling is accelerated – damaged bulbs are rapidly destroyed and a new hair bulb is thus formed at a surprising speed. As the hair is such a vital organ, cycling thus helps to keep the regeneration mode alive. Every single hair (2) is formed in the hair bulb deep in the lower part of hair follicle (1) of the hair. At the same time located at the very bottom of the follicle dermal papilla delivers to the bulb all the required nutrients from the capillary blood flow. Basically we can say all mature hair follicles have a permanent portion above the point of the hair muscle (3) and sebaceous gland (4) insertion and a transient portion below. Hair follicle is considered to be a separate outgrowth of the skin with its own metabolism and the processes of formation, interacting with the components of the skin and the epidermis. The follicle can be recognized as a tiny but powerful factory, which throughout the human life span hardly ever stops working. This hair shaft factory is unique in that it is the only organ in the mammalian body which, for its entire lifetime, undergoes cyclic transformations. The hair follicle cycles between phases of rapid growth (Anagen - A) to apoptosis-driven regression (Catagen - B) and back to Anagen, via an interspersed period of relative rest (Telogen - C). In many young mammals the Anagen growth phase occurs in a wave like pattern across the skin surface, but the hair follicles of humans can run through the normal cycles of growth apparently independently of neighboring follicles. In other words at any given time, a random number of hairs will be in various phases of growth and shedding. Hair is shed continually and renewed by the operation of these alternating cycles of growth, rest, fallout and renewed growth. Growth is not synchronized so each hair passes through these three phases independently. The relative duration of these phases varies with the individual’s age, nutritional status, hormonal factors, and other physiologic and pathologic factors. The duration of Anagen determines the final length of the hair, however it once again varies depending on particular individual and according to body site. Although we speak of phases in the development of a hair follicle, it should be made clear that these are actually dynamic, flowing processes and the setting up of phases is purely for our understanding of the human hair follicle cycle. Normally this cycle of hair production and inactivity will continue for the duration of the individual’s life but other factors can influence and inhibit hair production and in some cases lead to physical destruction of the hair follicle. Normally every single hair life span is affected by sex, age, hair type, nutrition, cosmetics, heredity and general health factors. Climate conditions, weather and seasonal variations also affect hair growth. Severe hair damage factors may include adverse reactions to drugs or as a result of scarring, tumors, radiation, the genetics of the individual, hormones and/or their immune system.