Afaf Ibrahim Meleis developed her Transition Theory over 50 years through extensive research on transitions in various contexts. She identified key concepts of the theory including types of transitions, patterns of transition, properties of transition, transition conditions, and patterns of response. Meleis' theory provides a framework for understanding the complexity of transitions and the role of nurses in facilitating healthy transitions. It has been applied in diverse areas such as immigration, aging, illness, and organizational change. The theory emphasizes the influence of individual and environmental factors on transition and identifies indicators of effective transition processes and outcomes.