This chapter provides an overview of how manufacturing systems have progressively evolved toward reconfigurable manufacturing systems (RMS) within the context of Industry 4.0. We focus on the key challenges in RMS design, the selection of reconfigurable system components, and process planning strategies in RMS environments. First, we offer a concise account of the historical shifts in production paradigms, highlighting the main drivers behind each transition. We then discuss the four industrial revolutions, setting the stage for next-generation manufacturing systems (NGMS). Among them, RMS is introduced with its fundamental principles and historical background. After presenting the six core characteristics of RMS that guide its design goals, we describe the various hardware components that can be reconfigured in an RMS. We then turn our attention to the evolution of computer-aided process planning (CAPP) in the RMS setting. Finally, we conclude by summarizing the essential insights related to RMS under Industry 4.0.