It’s a type of surgery that moves hair you already have to fill an area with thin or no hair. Doctors have been doing these transplants in the U.S. since the 1950s, but techniques have changed a lot in recent years.

You usually have the procedure in the doctor’s office. First, the surgeon cleans your scalp and injects medicine to numb the back of your head. Your doctor will choose one of two methods for the transplant: follicular unit strip surgery (FUSS) or follicular unit extraction (FUE).

With FUSS, the surgeon removes a 6- to 10-inch strip of skin from the back of your head. He sets it aside and sews the scalp closed. This area is immediately hidden by the hair around it.

Next, the surgeon’s team divides the strip of removed scalp into 500 to 2,000 tiny grafts, each with an individual hair or just a few hairs. The number and type of graft you get depend on your hair type, quality, color, and the size of the area where you’re getting the transplant.

If you’re getting the FUE procedure, the surgeon’s team will shave the back of your scalp. Then, the doctor will remove hair follicles one by one from there. The area heals with small dots, which your existing hair will cover.

After that point, both procedures are the same. After he prepares the grafts, the surgeon cleans and numbs the area where the hair will go, creates holes or slits with a scalpel or needle, and delicately places each graft in one of the holes. He’ll probably get help from other team members to plant the grafts, too.

Depending on the size of the transplant you’re getting, the process will take about 4 to 8 hours. You might need another procedure later on if you continue to lose hair or decide you want thicker hair.