Dr. William Rassman was educated in medicine and surgery at the Medical College of Virginia, the University of Minnesota, and Cornell and Dartmouth Medical Centers. He did a cardiovascular fellowship with Dr. C.W. Lillehei, the man who invented modern heart surgery. He served in the U.S. Army, reaching the rank of Major and served as a war surgeon in the Republic of Vietnam. He
volunteered to work at Vietnamese hospitals in a teaching capacity and as a surgeon. The American Board of Surgery certified Dr. Rassman in 1976.

In 1992, Dr. Rassman founded NHI Medical and quickly became a world leader in hair transplant technology, enabling surgeons to perform hair transplants with large numbers of very small grafts in single surgeries that looked totally natural for the very first time ever. He presented his breakthroughs at medical meetings around the world and published them in medical journals and in textbooks. He developed a strong stance on the ethics as he condemned doctors using sales tactics. Dr. Rassman pioneered the large session hair transplants as he was the first to perform 2000, 3000, and 4000 grafts in single session. The Follicular Unit Transplant (1995) and The Follicular Unit Extraction technology (2002) was pioneered by him.