We discuss the Theoretical Domains Framework (TDF), a tool for investigating behaviour change. The TDF is used in various studies to identify factors influencing behaviours, primarily in healthcare settings, but also in other contexts. The research uses qualitative and quantitative methods, including interviews, surveys, and systematic reviews, to explore barriers and facilitators to behaviour change. Studies explore the framework's application and refinement, examining optimal study design and data analysis techniques for different populations. The TDF aims to inform intervention design and improve the effectiveness of behaviour change initiatives.