Why does hair grow?

Hair grows because living cells at the root of each follicle keep making new cells. As the newer cells form, older ones are pushed upward, harden, and become the strand you can brush, braid, trim, or tuck behind an ear.

Each hair has its own schedule, which is why a child can lose some hairs today and still have plenty growing. Head hair usually stays in its growing phase far longer than eyebrow hair, so it can reach a much greater length.