Recent interest in exosomes derives from their characterisation as intercellular communication initiators able to mediate the horizontal and systemic transfer of genetic and protein material. In spite of its great potential in therapy and as non-invasive biomarkers of disease, there is little information about the molecular mechanisms that determine their biogenesis, binding and capture by target cells, or their function. The tetraspanins, which form microdomains that bind to the plasmatic membrane, are the most abundant proteins on the surface of exosomes. This project has the aim of using the large battery of tools against tetraspanins and their associated molecules created in our laboratory to study their functional role in the biogenesis and function of exosomes. With all of this we aim to gain deeper knowledge of exosome functions. This information is crucial to optimise therapies based on these exocytic vesicles, given that they will reveal new molecular targets that will allow us to either block their secretion, to reduce their metastatic and angiogenic capacities, or to increase their stability or immunoregulatory capacity.