Hair regrowth treatment may soon take a major leap forward, as researchers in a recent study have successfully grown complete, fully functional hair follicles outside of the living body, in a dish. This was made possible by the discovery of a previously unknown third cell type, the accessory mesenchymal cell population, which is essential for growing functional hair follicles. These specific supporting cells allow the follicle to grow deep into the skin, a process called downgrowth, to produce a proper hair shaft.