Abstract All cells in the body, including brain cells, release small vesicles that can be found in blood, cerebrospinal fluid, and even urine. Because each vesicle was released by a specific cell, their analysis can tell us about the cells from which they came, including whether that cell was infected, cancerous, or malfunctioning in some way. We will produce tools to analyze these vesicles to improve the ability to detect, treat, and prevent disease.