Follicular Unit Transplantation (FUT) is a hair restoration technique where a patient's hair is transplanted in naturally occurring groups of 1 to 4 hairs, called follicular units. Follicular units also contain sebaceous (oil) glands, nerves, a small muscle, and occasional fine vellus hairs. In Follicular Unit Transplantation these small units allow the surgeon to safely transplant thousands of grafts in a single session, which maximizes the cosmetic impact of the procedure.

FUT is considered an advance over older hair transplantation procedures that used larger grafts and often produced a pluggy, unnatural look. In a properly-performed follicular unit transplant, the results will mimic the way hair grows in nature and will be undetectable as a hair transplant.

Source: en.wikipedia.org/wiki/Follicular_unit_transplantation