Hildegard Peplau was the first nursing theorist published in over a century. She created the nursing theory of Interpersonal Relations, which focused on the nurse-patient relationship and revolutionized nursing as a scholarly discipline. Peplau drew from her experiences as a nurse and student of psychology to develop a theory based on empirical evidence from analyzing nurse-patient interactions. Her theory established concepts of nursing roles, phases of the relationship, and techniques like process recording that are still used in nursing education today.