Physicians, also called doctors, diagnose and treat illnesses, injuries, and chronic conditions. Physicians can specialize in a certain bodily system or function, such as cardiology (the heart and circulatory system) or nephrology (the kidneys and renal system). They can also choose to work with certain populations, like pediatricians, who treat children. Physicians work in hospitals, doctors’ offices, or surgery centers. They may also conduct research or work for the government or military. Becoming a physician requires considerable training and preparation, and involves several years of post-secondary education.