<p> Extracellular vesicles (EVs) are small, lipid compartments that function in the long-distance transport of proteins, nucleic acids and other metabolites. In mammals, EVs are important vehicles of intercellular communication and play a crucial role in modulating immune responses. Plant cells also secrete EVs, particularly in response to infection, but the contents of these vesicles have not been analyzed and their function is unknown. To better understand plant EVs and their roles in defense and signaling, I first pioneered methods for isolating and purifying EVs from the intercellular wash of <i>Arabidopsis </i> leaves. Secondly, I examined the protein and RNA contents of purified EVs. Proteomic analyses revealed that <i>Arabidopsis</i> EVs are enriched for defense- and stress-related proteins. Consistent with this finding, EV secretion was enhanced in response to biotic stress. Furthermore, a collaboration with Blake Meyer&rsquo;s laboratory at the Donald Danforth Plant Science Center identified several species of small RNA in purified EV samples, as well as a surprising enrichment for tiny RNAs (tyRNAs) 10 to 17 nt long. Finally, by examining the interactions between <i>Arabidopsis</i> EVs and the plant pathogenic fungus <i>Colletotrichum higginsianum</i>, I discovered that plant EVs associate with fungal structures and affect developing fungal morphology. Combined, my research represents a significant advancement in the field of plant EV research. It provides strong evidence for the involvement of plant EVs in the immune response and suggests they are capable of trafficking proteins and RNAs into invading pathogens.</p><p>