The chapter discusses the significant advancements in understanding the adsorption, pore condensation, and hysteresis behavior of fluids in nanoporous materials. These advancements have led to significant improvements in the structural characterization of these materials through physical adsorption techniques, particularly with the development of advanced theoretical procedures based on statistical mechanics, such as Non-Local Density Functional Theory (NLDFT) and molecular simulations. These methods allow for a more accurate and detailed analysis of adsorption and phase behavior at the molecular level. The chapter also reviews the major underlying mechanisms associated with these behaviors and their significance for advanced physical adsorption characterization. It highlights the importance of pore size analysis and the challenges posed by hysteresis in complex porous systems, emphasizing the need for accurate and reliable methods to characterize these materials. The chapter concludes by summarizing the progress made and the potential future directions in this field.The chapter discusses the significant advancements in understanding the adsorption, pore condensation, and hysteresis behavior of fluids in nanoporous materials. These advancements have led to significant improvements in the structural characterization of these materials through physical adsorption techniques, particularly with the development of advanced theoretical procedures based on statistical mechanics, such as Non-Local Density Functional Theory (NLDFT) and molecular simulations. These methods allow for a more accurate and detailed analysis of adsorption and phase behavior at the molecular level. The chapter also reviews the major underlying mechanisms associated with these behaviors and their significance for advanced physical adsorption characterization. It highlights the importance of pore size analysis and the challenges posed by hysteresis in complex porous systems, emphasizing the need for accurate and reliable methods to characterize these materials. The chapter concludes by summarizing the progress made and the potential future directions in this field.