There is a large demand for doctors across the world today, because people want to be healthy. The number of doctors has increased in recent years because more people have become aware of the importance of proper medical care. In the United States alone there are approximately 140 doctors for every 1000 population. A doctor, surgeon, obstetrician/ Gynecologist, psychiatrist, pediatrician, surgery room chief, radiologist, cardiologist, gastroenterologist, psychiatrist, surgeon, pediatrician, nurse practitioner, psychiatrist, and nurse practitioner, is a medical professional that practices internal medicine, that is concerned with treating, preventing, or curing illness, injury, and the development of new diseases through the investigation, diagnosis, treatment and prevention of disease, damage, and other bodily and mental impairments. Different doctors specialise in different fields of medicine. For instance, a psychiatrist may specialize in schizophrenia or bipolar disorder to a child psychologist might have specialization in autism or disorders associated with children. While doctors are required to complete an extensive amount of schooling before they can practise medicine, most others have started their careers as medical office assistants before progressing to a higher rank in the profession. As medical science continues to develop so will the number of doctors available to serve humanity. Today there are many ways that doctors make money. Some work in hospitals and are paid by the hospital for providing healthcare services. Other doctors work independently providing healthcare services to individuals or communities. The most common way that doctors make money comes from performing surgeries. Surgeons are required to have a college degree, whereas physicians who perform surgeries are not required to have a college degree but are usually highly trained medical professionals with many years of experience.