Exosomes are small extracellular vesicles (EVs) secreted by many cell types in 
both normal and pathogenic circumstances. Because EVs, particularly exosomes, 
are known to transfer biologically active proteins, RNAs and lipids between 
cells, they have recently become the focus of intense interest as potential 
mediators of cell-cell communication, particularly in long-range and juxtacrine 
signaling events associated with adaptive immune function and progression of 
cancer. Among the EVs, exosomes appear particularly adapted for long-range 
delivery of cargoes between cells. Because of their association with disease 
states, the exciting potential for exosomes to serve as diagnostic biomarkers 
and as target-specific biomolecule delivery vehicles has stimulated a broad 
range of biomedical investigations to learn how exosomes are generated, what 
their cargoes are, and how they might be tailored for uptake by remote targets. 
Addressing these questions requires experimental models in which biochemically 
useful amounts of material can be harvested, gene expression easily manipulated, 
and interpretable biological assays developed. The early Xenopus embryo fulfills 
these model-system ideals in an in vivo context: during morphogenesis the embryo 
develops several large, fluid-filled extracellular compartments across which 
numerous tissue-specifying signals must cross, and which are abundantly endowed 
with exosomes and other EVs. Importantly, certain surface-facing tissues avidly 
ingest EVs during gastrulation. Recent work has demonstrated that EVs can be 
isolated from these interstitial spaces in amounts suitable for proteomic and 
transcriptomic analysis. With its large numbers, great cell size, 
well-understood fate map, and tolerance of a variety of experimental approaches, 
the Xenopus embryo provides a unique opportunity to both understand and 
manipulate the basic cell biology of exosomal trafficking in the context of an 
intact organism.