Growth factors are released by dermal papilla cells at the base of the hair follicle and activate stem cells in the follicular bulge region. Activated stem cells may differentiate into matrix keratinocytes, migrate and proliferate to begin the formation of a new hair shaft in the proliferative phase. Both dermal papilla and stem cells are reliant on each other, and thus, when they interact through the stimulation of various growth factors, they give rise to the future follicular unit.