Updated project metadata. Extracellular vesicles have been the center of many studies focusing on neuron-to-neuron communication while the role of EVs in progenitor-to-neuron and -astrocyte communication occurring during brain development has not been systematically investigated. In this project, we focus on the physiological characterization, dynamic and function of human EVs during human brain development using human-derived cerebral organoids, neural progenitors, neurons and astrocytes. We examined the composition and function of EVs, in patients with myoclonic epilepsy and find alterations in size, composition and function. This study sheds new light on the biology of EVs during brain development.