Volume 05 provides a comprehensive exploration of the fundamental principles, properties, and dynamics of soil colloids and their pivotal role in soil chemistry and nutrient dynamics. Soil colloids, comprising clay minerals, organic matter, and iron and aluminium oxides, are minute particles with dimensions ranging from nanometres to micrometres. In this volume, we study the classification and characteristics of soil colloids, elucidating their surface properties, charge characteristics, and interactions with ions and water molecules. Understanding soil colloids is paramount for deciphering soil chemistry and nutrient dynamics, as these particles serve as the primary medium for ion exchange and nutrient retention in soils. Through a combination of theoretical frameworks, empirical models, and experimental evidence, we explore the mechanisms governing ion adsorption, desorption, and diffusion on soil colloids, shedding light on the factors influencing nutrient availability, plant uptake, and soil fertility. Moreover, this volume delves into the mathematical underpinnings of soil colloids, including the theories of electrostatics, surface chemistry, and surface complexation. By applying mathematical models and computational techniques, we unravel the complexities of soil colloid behavior, predicting their interactions with ions and organic molecules, and elucidating their role in soil biogeochemical processes. Furthermore, we explore advanced topics in soil colloids research, including theorems and mathematical-based concepts. By integrating theoretical insights with experimental evidence, we aim to advance our understanding of soil colloids and their implications for soil health, environmental sustainability, and ecosystem function. In essence, Volume 05 serves as a comprehensive resource for researchers, educators, and practitioners in soil science and related disciplines, providing insights into the complexities of soil colloids and ion exchange processes. Through rigorous analysis, empirical validation, and theoretical exploration, we aim to unravel the mysteries of soil colloids, empowering readers to unlock the potential of soils to support thriving ecosystems and sustainable agriculture.