Emergency medicine, also known as accident and emergency medicine, is the medical specialty concerned with the care of illnesses or injuries requiring immediate medical attention. Emergency physicians care for unscheduled and undifferentiated patients of all ages. As first-line providers, their primary responsibility is to initiate resuscitation and stabilization and to start investigations and interventions to diagnose and treat illnesses in the acute phase. Emergency physicians generally practice in hospital emergency departments, pre-hospital settings via emergency medical services, and intensive care units.