Lipid nanoparticles (LNPs) have emerged as leading non-viral carriers for messenger RNA (mRNA) delivery in clinical applications. This review discusses the structure and mechanisms of LNPs, their targeted delivery to various cells and tissues, and their applications in preventing infectious diseases, treating cancer, and addressing genetic diseases. LNPs are composed of ionizable cationic lipids, helper lipids, cholesterol, and polyethylene glycol (PEG) lipids, which enhance mRNA stability, cellular uptake, and cytoplasmic release. The review highlights the challenges in delivery efficiency, tissue targeting, toxicity, and storage stability, while emphasizing the potential of mRNA-LNP technology in disease treatment. Preclinical and clinical research progress is discussed, including the development of LNPs for targeting immune cells, liver, and extrahepatic tissues. The review also covers the therapeutic aspects of mRNA-LNP vaccines, particularly in cancer and infectious disease treatment, and the potential of mRNA-LNP technology in future research and clinical applications.Lipid nanoparticles (LNPs) have emerged as leading non-viral carriers for messenger RNA (mRNA) delivery in clinical applications. This review discusses the structure and mechanisms of LNPs, their targeted delivery to various cells and tissues, and their applications in preventing infectious diseases, treating cancer, and addressing genetic diseases. LNPs are composed of ionizable cationic lipids, helper lipids, cholesterol, and polyethylene glycol (PEG) lipids, which enhance mRNA stability, cellular uptake, and cytoplasmic release. The review highlights the challenges in delivery efficiency, tissue targeting, toxicity, and storage stability, while emphasizing the potential of mRNA-LNP technology in disease treatment. Preclinical and clinical research progress is discussed, including the development of LNPs for targeting immune cells, liver, and extrahepatic tissues. The review also covers the therapeutic aspects of mRNA-LNP vaccines, particularly in cancer and infectious disease treatment, and the potential of mRNA-LNP technology in future research and clinical applications.