Internal Medicine is a medical field that focuses on preventing, diagnosing, and treating internal diseases. Physicians who specialize in this field are called internists and are skilled in managing patients with complex or undifferentiated disease processes as well as ICU patients. Internists care for both hospitalized and ambulatory patients and may also be involved in teaching and research. They often work in hospitals due to the seriousness of their patients' conditions and may have subspecialty interests in specific organs or organ systems.