Anagen

• Hair naturally undergoes a cycle of growth, resting and shedding/regrowth, according to P&G Beauty Science. These three stages are known as anagen, catagen and telogen. Anagen is the main growth phase and is determined by your genetic makeup and nutrition. It can last for three years or more, and a hair can grow up to three feet. A single hair follicle grows several hairs over the average human's lifetime, thanks to vitamin B, which can be found in gelatin, fruits and vegetables.
  
  

Catagen

• During the catagen phase, the hair matrix, or initial bulb of hair cells, comes loose from the dermal papilla, where hair originates, toward the surface of the scalp at right about the time the hair is going to shed. This phase is marked by hair cells no longer reproducing and lasts two to three weeks. The hair follicle then shrinks and moves toward the surface.
  
  

Telogen

• Telogen is the regrowth phase, when the previous hair growth has stopped and new hair growth is beginning. After catagen occurs and the old hair has moved closer to your scalp's surface, a new hair starts growing from the dermal papilla, creating a new follicle. When it reaches the old hair, it pushes it out of the scalp completely. That's why it's normal to lose up to 100 hairs per day, which you typically notice when you brush or comb your hair. This is a natural process and doesn't signal that your hair is weak or unhealthy. Telogen lasts anywhere from two to four months, according to pantogar.com.