Tumor exsome-mediated cell-cell communication has grown increasingly important in cancer research. Recent findings on vesicle-based information transfer by exosomes have changed our view of the tumor microenvironment. Â{u3D72}rrently, exosomes represent the main extracellular processes implicated in the regulation of multiple physiological processes. Importantly, in cancer, exosomes contribute to the formation of the tumor microenvironment, promoting invasion, angiogenesis, immune regulation and metastasis. Therefore, exosomes could be considered one of the major forces acting locally or systemically to promote the continuous crosstalk between the tumor and its microenvironment, influencing the behavior of different cell types such as stromal, endothelial and bone marrow-derived cells. Given the ability of exosomes to export unneeded endogenous molecules from cells, these structures hold great potential as anticancer therapeutic agents. This volume gives a comprehensive review on current research in this area and also discuss future prospects as prognostic markers for cancer.