This introduction presents an overview of key concepts discussed in the subsequent chapters of the book. The book addresses the fundamentals of passive microwave remote sensing of ocean environment. It focuses on detailed description of the physical principles, methodology, theory, and practice of ocean microwave observations. The book offers a first look at microwave detection capabilities. It emphasizes a number of important scientific topics and results related to hydrodynamics, electrodynamics, physics-based modeling, data analyses, and interpretation. The book provides advanced remote sensing studies of ocean environment. It also provides insight into the research and specification of hydrodynamic and electromagnetic effects, contributions, and signatures potentially observable by passive microwave radiometric sensors. The book explores the capabilities and advantages of high-resolution multiband passive radiometry and imagery for the detection of ocean variables and dynamic features.