Early-onset refers to the occurrence or development of a condition, disease, or disorder at a younger age than usual. In the context of research, early-onset typically refers to the study of conditions that manifest in individuals at a young age, such as early-onset Alzheimer's disease, early-onset puberty, or early-onset diabetes. Research in this area aims to understand the underlying causes, risk factors, and potential treatment options for these conditions that occur earlier in life than expected. This research is important for improving diagnosis, treatment, and prevention strategies for individuals who experience early-onset conditions.