Final answer:
The anagen phase is where hairs are actively growing, and it's in this phase that around 90 percent of your hair is growing at any given time. The rate of growth during this phase is 0.3 mm per day. The cycle repeats with new hair replacing the old ones.
Step-by-step explanation:
The growth cycle of hair occurs in three distinct phases: the anagen phase, the catagen phase, and the telogen phase. During the anagen phase, cells divide rapidly at the root of the hair, causing the hair shaft to be pushed up and out. It's in this phase which lasts anywhere between 2 to 7 years, that around 90 percent of your hair is growing at any given time.
The catagen phase, which lasts only 2 to 3 weeks, is a transition phase marking an end to the active growth of the hair follicle. The telogen phase is when the hair follicle is at rest and there is no new growth. This phase lasts about 2 to 4 months and at its end, another anagen phase begins, thus repeating the cycle.
The rate at which hair grows during the anagen phase is about 0.3 mm per day and on average, 50 hairs are lost and replaced each day. Hair loss occurs when the number of hairs shed exceeds what is replaced, which can be due to hormonal or dietary changes or even the aging process.
Learn more about Anagen Phase