Derma Rolling (also known as Micro needling) works a couple of ways, firstly, it assists Regrow Hair Tonic to penetrate the scalp deeper, getting right to the root of your follicles. Secondly, by breaking the epidermal layers it triggers your skin to produce more collagen and blood flow, thereby creating a better environment for hair growth. Best used in conjunction with Regrow Shampoo, Conditioner & Tonic!