Follicular units are distinct groupings of usually one to four terminal hairs.The follicular unit is thus a naturally occurring physiologic, as well as an anatomic entity. Follicular unit transplantation offers the surgeon the ability to transplant the maximum amount of hair with the minimum amount of non-hair bearing skin. In this way, recipient wounds are kept small, healing is facilitated, and with proper technique, large numbers of grafts may be safely moved per session.
The use of these units helps to ensure that the cosmetic result of the transplant will appear completely natural. In contrast to follicular units, micrografts (1-2 hairs), and mini-grafts (3-6 hairs), are small grafts cut randomly from donor hair, not specifically as individual intact follicular units. These multiple units will contain extra skin that will demand larger recipient sites, which, in turn, causes more wounding to the recipient bed and may limit the number of grafts that can safely be transplanted in a session.