Madeleine Leininger developed the Transcultural Nursing Theory, also known as the Culture Care Theory. She was the first to coin the concept of "culturally congruent care" and established transcultural nursing as a discipline. Her theory focuses on providing culturally appropriate nursing care by understanding patients' cultural values, beliefs, and lifeways. She developed the Sunrise Model to demonstrate the relationships between concepts like culture, care, health, and nursing. Leininger's work transformed nursing by emphasizing the importance of understanding culture in patient care.