Cyber-physical production systems (CPPS) allow for information exchanges within and between systems, providing the foundation for a higher local intelligence and the ability to selforganize and selfadapt to changing environmental conditions. These system features go hand in hand with a redefinition of the roles, responsibilities, and specific tasks of the people operating a CPPS. Instead of being mere supervisors, operators have to act as competent problem solvers and decision makers. Therefore, CPPS interfaces should support them in understanding the system's current state and constraints, and enable them to use this knowledge in deriving appropriate solutions for new and unexpected situations. The chapter identifies complexity and flexibility as two major challenges for the human-machine cooperation in CPPS. Based on these challenges, a set of design goals is suggested and how findings from human factors research can contribute to translating these goals into practice are illustrated.