Nursing is a profession within the health care sector focused on the care of individuals, families, and communities so they may attain, maintain, or recover optimal health and quality of life. Nurses may be differentiated from other health care providers by their approach to patient care, training, and scope of practice. Nurses practice in many specialties with differing levels of prescription authority. Nurses comprise the largest component of most healthcare environments; but there is evidence of international shortages of qualified nurses. Many nurses provide care within the ordering scope of physicians, and this traditional role has shaped the public image of nurses as care providers. Nurse practitioners are however permitted by most jurisdictions to practice independently in a variety of settings. Since the postwar period, nurse education has undergone a process of diversification towards advanced and specialized credentials, and many of the traditional regulations and provider roles are changing.