Doctors of internal medicine ("internists") focus on adult medicine and have had special study and training focusing on the prevention and treatment of adult diseases. At least three of their seven or more years of medical school and postgraduate training are dedicated to learning how to prevent, diagnose, and treat diseases that affect adults. Internists are sometimes referred to as the "doctor's doctor," because they are often called upon to act as consultants to other physicians to help solve puzzling diagnostic problems. While the name "internal medicine" may lead one to believe that internists only treat "internal" problems, this is not the case. Doctors of internal medicine treat the whole person, not just internal organs.