The use of both scalp flaps, in which a band of tissue with its original blood supply is shifted to the bald area, and free grafts dates back to the 19th century. Modern transplant techniques began in Japan in the 1930s, where surgeons used small grafts, and even “follicular unit grafts” to replace damaged areas of eyebrows or lashes, but not to treat baldness.
Their efforts did not receive worldwide attention at the time, and the traumas of World War II kept their advances isolated for another two decades. The modern era of hair transplantation in the western world was ushered in the late 1950s, when New York dermatologist Norman Orentreich began to experiment with free donor grafts to balding areas in patients with male pattern baldness. Previously it had been thought that transplanted hair would thrive no more than the original hair at the “recipient” site.
Dr. Orentreich demonstrated that such grafts were “donor dominant,” as the new hairs grew and lasted just as they would have at their original home. Advancing the theory of donor dominance, Walter P. Unger, M.D. defined the parameters of the “Safe Donor Zone” from which the most permanent hair follicles could be extracted for hair transplantation. As transplanted hair will only grow in its new site for as long as it would have in its original one, these parameters continue to serve as the fundamental foundation for hair follicle harvesting, whether by strip method or FUE.
For the next twenty years, surgeons worked on transplanting smaller grafts, but results were only minimally successful, with 2–4 mm “plugs” leading to a doll’s head-like appearance. In the 1980s, Uebel in Brazil popularized using large numbers of small grafts, while in the United States Dr. William Rassman began using thousands of “micrografts” in a single session. [Source: Wikipedia]