This chapter explores theoretical frameworks including cognitive science, system thinking, and sociotechnical systems, illustrating the evolution of UX from simple usability to encompass emotional, attitudinal, and behavioural dimensions of user interactions with technology. The chapter highlights the challenges of designing inclusive technologies that accommodate a wide array of user demographics, abilities, and cultural backgrounds. It emphasises the shift from human–machine interface (HMI) to human–machine cooperation (HMC), advocating for technology that supports cooperative interactions rather than mere functionality. Central themes include the integration of advanced technologies such as AI and machine learning, and their impact on the development of responsive, adaptive UX that anticipates user needs. The discussion extends into industry-specific applications, showcasing how UX principles are applied in health care, automotive, and sustainable energy sectors to enhance interaction and efficiency. The chapter proposes a system thinking approach in UX design, promoting a holistic view that recognises complex user interactions within service ecosystems. It concludes by reflecting on the ethical dimensions of UX design, stressing the importance of privacy, security, and inclusivity in creating technology that aligns with human values and needs.