These were developed as a concept in the late 1980s, the notion of “system” to capture the nature of research and innovation has exerted a strong influence on research, technology and innovation policy during the past two decades. In most systems approaches to STI, emphasis is put on the importance of interactions between different types of actors, and of the institutions guiding and framing these interactions. Developed initially as a synthesis of previous actor-centred approaches, more recently the notion of functions of (research and) innovation systems has been introduced. Depending on the respective emphasis put on different driving forces, authors speak of innovation systems, research and innovation systems, or science, technology and innovation systems.