We delve deep into the principles of both single-phase and two-phase systems, providing a clear roadmap from theoretical concepts to real-world applications. Beyond the technical specifics, this book explores the significant economic and environmental advantages that immersion cooling offers, from dramatically improving Power Usage Effectiveness (PUE) to enabling meaningful waste heat recovery. It is a work that not only explains the "how" but also the "why," making a compelling case for a technology that is poised to redefine the future of data centers.