In this position paper we argue that the availability of big monitoring data on Cyber-Physical Systems (CPS) is chal- lenging the traditional CPS modeling approaches by violat- ing their fundamental assumptions. However, big data also brings unique opportunities in its wake by enabling new modeling and analytics approaches as well as facilitating novel applications. We highlight a few key challenges and opportunities, and outline research directions for addressing them. To provide a proper context, we also summarize CPS modeling approaches, and discuss how modeling and ana- lytics for CPS differs from general purpose IT systems.