Cyber-physical systems (CPSs) are an increasingly known set of technologies and applications promising to enable manufacturing firms improving their responsiveness to deal with the unpredictability of market requirements. Indeed, from an operational perspective, responsiveness can be achieved because CPSs are an enabler of the reconfigurability of factories. Reconfigurability is a capability that has been theorized since almost two decades. Therefore, today we can consider such grounded theory as a lens to frame emerging CPS-related knowledge. This paper is an effort to give a contribution in this direction. In particular, starting from the acknowledgement that a relevant characteristic of reconfigurability is modularity, this research proposes a literature-based analysis of the Cyber-Physical Systems of the future smart factory.