The follicular unit is a living unit with muscle, nerves and blood vessels that are all tiny enough to fit into this small package. The unit is set off by a band of collagen that holds it together. If you look under a microscope at a scalp, you can see follicular units growing in just this way. The idea of bringing this information into hair transplant procedures led to innovative surgical methods. Once the surgeon has made all the hair transplant incisions that lay out the design he has created, the specially trained surgical team steps in. They use his plan to accomplish his goals, and in turn the goals of the patient. The groundwork is done for them by the surgeon when he does his incisions. Based on the fact that the average Caucasian male has a density of 2 hairs per millimeter, it can be assumed that the average density of hair is 1250 hairs per square inch. Figuring at an average of 2 hairs per follicular unit, it would take 625 follicular units per square inch. To get 25% of that, you would need 156 follicular units per square inch. This is very important, because knowing where the donor hair for the hair transplant will come from is imperative. The doctor will also want to know the patterns of baldness and hair growth in your family history. This will give an idea of whether there is hope for a good result that will last for a fair amount of time. The most common donor site for hair transplant surgery is on the head. If the sides and back of your head have full lustrous hair, you are in luck. This hair can be used as donor hair to replace hair you have lost on your balding spots. If your hair in these areas is not healthy, you face a difficult problem - where does the surgeon get the hair? The difference is that these procedures are generally more painful. 6. The grafts may not survive. Few surgeons will divulge to you the fact that hair grafts do not always survive after hair transplant surgery. The hope is that only a few will be lost and the overall result will not suffer. The reality is that is what usually happens.