Immune cell secreating exosomes. Exosomes are small, about 100 nm cell-derived vesicles, that carry RNAs and proteins and play crucial role in cell-cell interactions, communication and signalling. Exosomes attracted significant attention in past few years as a promissing platform for drug delivery to treat various diseases, including cancer, Parkinson's and others. They are formed inside the cells in so called multivesicular bodies, which fuse with plasma membrane and release hundreds of exosomes at once.