Nursing informatics integrates nursing, computer science, and information science. It aims to promote health through information and communication technologies. Theory is important for nursing informatics as an emerging discipline. Kurt Lewin's change theory and diffusion of innovation theory can be applied to nursing informatics. Lewin's theory involves three stages - unfreezing, changing, and refreezing. Diffusion of innovation theory explains how innovations spread through populations over time. Both theories can help understand and guide changes in nursing informatics.