Exosomes are small membrane-bound vesicles derived from endocytic compartments, released by many cell types. They differ from microvesicles, which are produced by plasma membrane shedding and are larger. Exosome biogenesis involves inward budding from multivesicular bodies (MVBs), resulting in intraluminal vesicles containing distinct proteins. Exosomes contain functional microRNAs (miRNAs) and small RNA, but little mRNA. Exosomes are specialized in carrying small RNA, including miRNAs, and can transfer these to recipient cells. In a co-culture system, exosomes from Epstein Barr virus (EBV)-infected cells were transferred to uninfected cells, delivering EBV-encoded miRNAs to sites of gene repression. EBV-miRNAs were also detected in non-infected cells in peripheral blood, indicating intercellular transfer. These findings suggest that exosomes may facilitate miRNA-based communication, important for immune responses and tumor microenvironments. Exosome secretion is regulated by Rab GTPases, and the loading of miRNAs into exosomes may be controlled by specific proteins. Exosomes may also be involved in the transfer of functional proteins between immune cells. Viruses like HIV and EBV may exploit exosome pathways for persistence. Exosome-mediated RNA transfer offers advantages over soluble factors, allowing simultaneous suppression of multiple genes. EBV, which infects 90% of the world population, may have co-opted exosome pathways for its survival.Exosomes are small membrane-bound vesicles derived from endocytic compartments, released by many cell types. They differ from microvesicles, which are produced by plasma membrane shedding and are larger. Exosome biogenesis involves inward budding from multivesicular bodies (MVBs), resulting in intraluminal vesicles containing distinct proteins. Exosomes contain functional microRNAs (miRNAs) and small RNA, but little mRNA. Exosomes are specialized in carrying small RNA, including miRNAs, and can transfer these to recipient cells. In a co-culture system, exosomes from Epstein Barr virus (EBV)-infected cells were transferred to uninfected cells, delivering EBV-encoded miRNAs to sites of gene repression. EBV-miRNAs were also detected in non-infected cells in peripheral blood, indicating intercellular transfer. These findings suggest that exosomes may facilitate miRNA-based communication, important for immune responses and tumor microenvironments. Exosome secretion is regulated by Rab GTPases, and the loading of miRNAs into exosomes may be controlled by specific proteins. Exosomes may also be involved in the transfer of functional proteins between immune cells. Viruses like HIV and EBV may exploit exosome pathways for persistence. Exosome-mediated RNA transfer offers advantages over soluble factors, allowing simultaneous suppression of multiple genes. EBV, which infects 90% of the world population, may have co-opted exosome pathways for its survival.