Although often invisible to the naked eye, plankton are fundamental to aquatic ecosystems. These microscopic organisms sustain intricate food webs and drive essential processes like carbon cycling and oxygen production, profoundly influencing the planet. This book explores their fascinating world, combining cutting-edge research with practical insights to highlight their ecological significance and innovative applications. Divided into three thematic sections, the book opens with an exploration of plankton ecology, examining their diversity, interactions, and the environmental factors shaping their behavior. Case studies illustrate long-term shifts in phytoplankton communities and the triggers of harmful algal blooms, providing a foundation for understanding global aquatic ecosystems. The second section shifts to marine and coastal environments, revealing the complex relationships between plankton and their habitats. The final section presents innovations in plankton research, covering mathematical models for optimizing cultivation and the discovery of commercially valuable bio-compounds. These innovations showcase how plankton science is addressing climate change, resource scarcity, and sustainability. Authored by an international team of experts, this book provides a comprehensive resource for researchers, students, and professionals in ecology, environmental science, and biotechnology. By exploring both the ecological roles of plankton and their potential for innovation, readers will gain new insights into these microscopic organisms, understanding their significant impact on the planet and their potential to drive sustainable solutions.