This review discusses the endocytosis and exocytosis mechanisms of functionalized nanoparticles in mammalian cells, emphasizing their importance in drug delivery and therapeutic applications. The article highlights the role of nanoparticle size, shape, and surface chemistry in determining their cellular uptake and clearance. It explains that endocytosis is crucial for targeting nanoparticles to disease sites, while exocytosis is essential for removing them from the body. The review covers various endocytosis pathways, including clathrin-mediated, caveolae-mediated, phagocytosis, and pinocytosis, and discusses how nanoparticle properties influence these processes. Factors such as nanoparticle size, surface charge, and shape significantly affect their interaction with cells. The study also explores the impact of nanoparticle aggregation and surface modifications, such as PEGylation, on their stability and cellular uptake. The review emphasizes the need to understand these mechanisms to design safe and efficient nanoparticles for drug delivery. It also discusses the exocytosis of nanoparticles, highlighting the importance of studying their release from cells to ensure biosafety. The article concludes that further research is needed to fully understand nanoparticle endocytosis and exocytosis to improve their therapeutic applications.This review discusses the endocytosis and exocytosis mechanisms of functionalized nanoparticles in mammalian cells, emphasizing their importance in drug delivery and therapeutic applications. The article highlights the role of nanoparticle size, shape, and surface chemistry in determining their cellular uptake and clearance. It explains that endocytosis is crucial for targeting nanoparticles to disease sites, while exocytosis is essential for removing them from the body. The review covers various endocytosis pathways, including clathrin-mediated, caveolae-mediated, phagocytosis, and pinocytosis, and discusses how nanoparticle properties influence these processes. Factors such as nanoparticle size, surface charge, and shape significantly affect their interaction with cells. The study also explores the impact of nanoparticle aggregation and surface modifications, such as PEGylation, on their stability and cellular uptake. The review emphasizes the need to understand these mechanisms to design safe and efficient nanoparticles for drug delivery. It also discusses the exocytosis of nanoparticles, highlighting the importance of studying their release from cells to ensure biosafety. The article concludes that further research is needed to fully understand nanoparticle endocytosis and exocytosis to improve their therapeutic applications.