This comprehensive guide is designed for researchers, professionals, and students looking to deepen their knowledge of diatoms, including detailed information on diatom photosynthesis regulation at the molecular scale, as well as their significant ecological roles, all aimed at promoting sustainable advancements and the safeguarding of aquatic ecosystems. Diatoms exert an immense influence on the ecosystem of Earth due to their remarkable abundance and species diversity. Thriving in diverse habitats spanning the oceans, intertidal benthic zones, saline and freshwater environments, and even terrestrial niches like moist soil, forests, and caves, they play an integral role. Diatoms alone account for around 20% of the oxygen generated by photosynthesis, comparable to the combined productivity of tropical rainforests worldwide, while their primary production can reach 40–45% in marine ecosystems. Nevertheless, in contrast to the extensive research on macroscopic photosynthetic organisms, investigations in this domain remain comparatively limited, despite the role of diatoms in global biogeochemical processes. This book presents an exhaustive review of the subject matter, encompassing a wide spectrum of topics ranging from the intricate molecular mechanisms of diatom photosynthesis and light absorption to the dominant role of diatoms as primary producers within ecological frameworks. Beyond this, the book delves into the practical implications stemming from diatoms and their photosynthetic productivity. A strong emphasis is placed on the importance of fundamental research in deepening our understanding of the natural world around us. Diatoms Photosynthesis provides readers with a comprehensive guide to understanding the fundamentals of diatom photosynthesis and their ecological significance in aquatic ecosystems; a guide to the potential of diatom-derived products for sustainable technologies; a roadmap from diatom photosynthesis to implications in applied sciences; a bridge to span the gap between fundamental research on diatoms and their practical applications. Audience This book caters to academic professionals, students, and researchers in the fields of marine biology, ecology, microbiology, and biochemistry. It offers insights and benefits into diatom photosynthesis, diatom physiology, biodiversity, ecosystem health, and sustainable technological advancements.