Service systems produce all services of significance and scope, yet the concept of service system is not well articulated in the service literature. This paper presents three interrelated frameworks as a first cut at the fundamentals of service systems. These frameworks identify basic building blocks and organize important attributes and change processes that apply across all service systems. Although relevant regardless of whether a service system uses IT, the frameworks are also potentially useful in visualizing the realities of moving toward automated service architectures. This paper uses two examples, one largely manual and one highly automated, to illustrate the potential usefulness of the three frameworks, which can be applied together to describe, analyze, and research how service systems are created, how they operate, and how they evolve through a combination of planned and unplanned change.