Endocytosis is a crucial process in cells, involving the internalization of various substances and their subsequent processing, recycling, or degradation. This review focuses on the classical endocytic pathway and the maturation of late endosomes (LEs) into multivesicular bodies (MVBs). The maturation process involves significant changes that disconnect LEs from early endosomes and prepare them for their role as a feeder pathway to lysosomes. Key steps include the switch from Rab5 to Rab7, phosphatidylinositol (PI) conversion, Arf1/COP1 association, intralumenal vesicle (ILV) formation, acidification, and changes in luminal ionic environment. The formation of ILVs is particularly important for the selective sorting of membrane-associated cargo for degradation and the maturation of LEs. The review also discusses the role of specific proteins and complexes, such as the ESCRT machinery, in these processes. Understanding endosome maturation is essential for comprehending cell life and disease, as well as for studying host cell entry by animal viruses.Endocytosis is a crucial process in cells, involving the internalization of various substances and their subsequent processing, recycling, or degradation. This review focuses on the classical endocytic pathway and the maturation of late endosomes (LEs) into multivesicular bodies (MVBs). The maturation process involves significant changes that disconnect LEs from early endosomes and prepare them for their role as a feeder pathway to lysosomes. Key steps include the switch from Rab5 to Rab7, phosphatidylinositol (PI) conversion, Arf1/COP1 association, intralumenal vesicle (ILV) formation, acidification, and changes in luminal ionic environment. The formation of ILVs is particularly important for the selective sorting of membrane-associated cargo for degradation and the maturation of LEs. The review also discusses the role of specific proteins and complexes, such as the ESCRT machinery, in these processes. Understanding endosome maturation is essential for comprehending cell life and disease, as well as for studying host cell entry by animal viruses.