||Globally, the subject of exosomes (defined as extracellular nano-vesicles (30 nm to 130 nm in diameter) secreted by many types of living cells and found in all body fluids, including blood, urine, and saliva) has received significant attention over the past 15 years, but with more intensive research during the last five years. The promising future of exosomes in diagnostics and therapeutics can be seen through the growing number of acceptable clinical trials using exosomes, mainly for the early-stage detection of cancer. This research on exosomes involves two projects: The first project is to characterize tumor exosomes secreted by female breast cancer cells (MCF-7) using three biophysical properties (size, mass, and density) that are correlated to one molecular property: the level of miR21, a standard cancer biomarker. Our developed approach revealed that tumor (MCF-7) exosomes are heterogeneous in miR21. The second project aims to characterize exosomes through the influence of their thermal stability. Using our approach, Time-Temperature Method (TTM), we were able to demonstrate that distinguishing tumor (MCF-7) and normal-like (MCF-10A) exosomes by their thermal stability is possible with 33% average difference and a significant statistical result (P-value < 0.001). Accordingly, our results show, for the first time to our knowledge, that exosome-thermal stability is an important biophysical property for differentiation between different populations of exosomes. The new methods and results presented in this study could, with further research, be developed into a point-of-care device for the early detection of cancer.