Hair growth occurs in a cyclical process with three distinct phases: anagen, catagen, and telogen. The anagen phase is the growth period, where hair cells rapidly divide, lengthening the hair shaft. This phase can last several years and largely determines the length of hair. Following anagen is the catagen phase, a transitional period that lasts a few weeks, during which the follicle shrinks and hair growth slows down. The final stage, telogen, is a resting period of about three months, after which the hair falls out, and the follicle re-enters the anagen phase, beginning the cycle anew. Genetics, age, nutrition, and hormonal balance significantly influence these phases, affecting hair growth rate and pattern.