With 5G being a reality, what will 6G be? Extensive discussions have been initiated around possible paradigm shifts and new technologies for 6G in recent years. With this summer school, we aim at providing a comprehensive roadmap about fundamental theory, emerging applications, and possible enabling technologies for 6G. The summer school consists of both application-domain talks with a high-level overview of key elements and practical aspects of 6G systems, and in-depth technical lectures focusing on theoretical aspects of emerging research directions. The lectures are organized around several key components of current 6G research trends, including the intersection between Artificial Intelligence (AI) and wireless communications, cyber-physical systems, semantic communications, Internet of Things (IoT) and massive access, integrated space-air-ground systems, mmWave and Terahertz communication, integrated sensing and communication, and security and trustworthiness of 6G systems.