Chapter 4 introduces the essential digital technologies underpinning digital transformation. The presentation of each technology is concise yet clear, enabling a better understanding of its core essence. The chapter covers a wide range of emerging technologies, including 5G/6G mobile communications, the Internet of Things (IoT), cloud and edge computing, augmented reality (AR), virtual reality (VR), metaverse, digital twins, big data analytics, bioinformatics, cybersecurity solutions, robots, robotic process automation (RPA), autonomous driving, drones, blockchain, cryptocurrencies (such as Bitcoin), Web 3.0, 3D/4D printing, quantum computing, and artificial intelligence (AI).