Nanosized extracellular vesicles called exosomes can interact with or transfer their cargo into the recipient cells, which regulates signaling between tumor cells and bone marrow stromal cells in the tumor microenvironment. Tumor-derived exosomes affect cell adhesion, angiogenesis, cancer metastasis, and cancer chemoresistance. Effectiveness of dendritic-derived exosomes in mediating tumor immunity have been tested in clinical trials. Meanwhile, autologous exosomal components obtained from patients have potential as diagnostic biomarkers in cancer, but isolation/identification techniques for exosome samples are critical for optimal individual health decisions. In this seminar, I will focus on the biological function of exosomes in tumor microenvironment. In addition, I also want to briefly introduce research on exosomes in our lab.