Human hair growth a new strand of hair begins to form. The rate or speed of hair growth is about 1.25 centimetres or 0.5 inches per month, or about 15 centimetres or 6 inches per year. The anagen phase is known as the growth phase. This is the phase where the hair physically grows approximately 1 cm per month. It begins in the papilla and can last from two to six years. The span at which the hair remains in this stage of growth is determined by genetics. The longer the hair stays in the anagen phase, the longer it will grow. During
Human hair color years old, 74% had some grey hair, covering an average of 27% of their head, and approximately 1 in 10 people had no gray hairs even after the age of 60. Children born with some hair colors may find it gradually darkens as they grow. Many blond, light brown, or red haired infants experience this. This is caused by genes being turned off and on during early childhood and puberty. Changes in hair color typically occur naturally as people age, eventually turning the hair gray and then white. This is called achromotrichia. Achromotrichia normally begins in the early to mid-twenties