RHIC Beam Energy Scan Program and Beyond

Since 2010, STAR Collaboration has undertaken the Beam Energy Scan (BES) program at the Relativistic Heavy Ion Collider (RHIC) in order to understand the QCD phase structure. Over a wide energy range, from 3 to 200 GeV Au+Au collisions, the RHIC BES program has recorded the world largest datasets. Despite of challenges in colliding gold ions at the energy that is two orders of magnitude lower than the designed one, the campaign on data taking has completed successfully and the physics analysis is underway. In this talk, I will present selected results from the first phase of the BES with focus on collective dynamics and fluctuations in high-energy nuclear collisions. Physics implications of these results and future prospects, especially the QCD phase structure at the high baryon density region, will be discussed.