Nursing has evolved from an occupation to a profession over centuries. It began as providing informal care and evolved with the establishment of nursing orders in the Christian era. Florence Nightingale professionalized nursing in the 1800s by establishing nursing schools and emphasizing hygiene. She viewed nursing as both a science and an art. In the 20th century, nursing continued developing specialized roles and becoming more research-based. Nursing is now a well-established profession worldwide, guided by codes of ethics.