This is the first of three Books that together provide an integrated picture of the Aegean Sea, presenting the natural components of the system (Book I and Book II) as well as the human presence in the extended area (Book III). The Aegean Sea, also called Aegean Archipelagos, is an open, complex, and diverse marine system situated between the Black Sea and the Eastern Mediterranean, with different compartments and interactions. This book provides an in-depth exploration of the Aegean Sea's natural systems, shedding light on its geodiversity, geological dynamics, air-land-sea interaction, hydrology, suspended matter and sediments. Divided into 4 parts, the book introduces the diversity, geological dynamics, and evolution of the natural system of the Aegean Sea (Parts 1 and 2), followed by a section devoted to the land-sea interaction in the Aegean coastal system where experts in the field explore freshwater and matter inputs into the Aegean coastal system, as well as the coastal morphodynamics and evolution of the Aegean Sea, its adjacent land areas, and islands. In Part 3, the book delves into the air-sea interaction over the Aegean Sea, presenting its intricate dynamics, including heat and freshwater fluxes, wind waves, tides, and atmospheric deposition. The book closes with a section focused on the hydrology, chemistry, and dynamics of water masses and the sea bottom, providing insights into suspended matter and fluxes, sediments, climate changes, and the intricate nutrient and carbon dynamics within the Aegean Sea ecosystem (Part 4). Given the breadth and depth of its coverage, this book serves as a valuable resource for researchers, scholars, and students interested in marine geology, oceanography, and environmental analysis, as well as policymakers and conservationists seeking a comprehensive understanding of the Aegean Sea's complex natural systems.