Anagen is the active growth phase of the hair cycle, during which hair follicles produce new hair. This phase can last several years, depending on factors like genetics and health. During anagen, the hair shaft is formed, and the hair grows longer and thicker. The duration of the anagen phase varies among individuals and different body areas. For example, scalp hair may remain in anagen for 2 to 7 years, while body hair has a much shorter anagen phase. Understanding anagen is essential for studying hair growth patterns and conditions like alopecia.