The ExoMir™ Kit is designed for the fractionation of, and RNA extraction from, exosomes and other microparticles in cell-free fluids. The ExoMir Kit uses a rapid fractionation approach in which samples are passed over syringe filters to capture exosomes and larger membrane-bound particles. The filters are then flushed with an RNA extraction reagent to lyse the captured particles and release their contents. In the standard procedure, samples are passed over 2 filters connected in series, to effectively capture particles such as apoptotic bodies, microvesicles on the upper filter and exosomes on the lower filter. Then the filters are disconnected and separately flushed with BiooPure™-MP to lyse the captured particles and release their contents. BiooPure-MP is a single-phase RNA extraction reagent containing guanidinium thiocyanate and phenol, which has been optimized to provide maximal recovery of the low-mass amounts of RNA in microparticles. Recovery of RNA is further improved by using the inert co-precipitant (linear acrylamide) included in the kit. Cell-free fluids that can be processed with the ExoMir™ Kit include blood serum, cerebrospinal fluid, and eukaryotic cell culture media (“conditioned media”). Recent research has highlighted the role of small membrane-bound particles such as exosomes and microvesicles, as intercellular mediators of biological information. Traditional methods for recovering exosomes involve centrifuging liquid samples at increasing centrifugal force, to sequentially pellet the larger and smaller particles. Traditionally to recover exosomes, ultracentrifugation of samples at relative centrifugal force of at least 100,000 x g for several hours or more is required.