The Open Radio Access Network (RAN) paradigm and its embodiment based on the O-RAN Alliance specifications is poised to transform the telecom ecosystem via virtualized and disaggregated RAN, open interfaces and RAN intelligent controllers (RICs). This talk will provide a comprehensive introduction to O-RAN, including a clear overview of the potentials of the Open RAN paradigm and of the challenges to its realization. After a brief introduction on O-RAN and its architecture, we will focus our attention on discussing how Artificial Intelligence (AI) and data-driven optimization will transform the ecosystem and will identify challenges to be overcome to de-risk AI, as well as how to design, train and deploy AI-based solutions that are able to generalize across multiple topologies, network and traffic conditions. Finally, the talk with focus on showcasing selected results obtained using OpenRAN Gym (https://openrangym.com/), an experimental platform for research on O-RAN developed by our team at Northeastern University.Â