There are two types of physicians: the MD (or medical doctor) or the DO (or doctor of osteopathic medicine. They diagnosis illnesses and prescribe and administer treatment for people suffering from injury or disease. As physicians, they are among the highest paid and most respected of all professionals. They are also among the most rigorously trained: 4 years of college, 4 years of medical school, and 3 years of hospital internship and residency is the minimum requirements. Still more training is required for those who choose to specialize. The hours can be long and the paperwork, required by health insurance companies and government agencies, can be extensive. Physicians often have to make - what are quite literally - life and death decisions. Yet few experiences are more satisfying than easing someone's pain, fixing a broken body, or bringing a new baby into the world. Being an MD or DO may be demanding, but it also can be one of the most rewarding professions.