Exosomes are nanosized membrane particles that are secreted by cells that 
transmit information from cell to cell. The information within exosomes 
prominently includes their protein and RNA payloads. Exosomal microRNAs in 
particular can potently and fundamentally alter the transcriptome of recipient 
cells. Here we summarize what is known about exosome biogenesis, content, and 
transmission, with a focus on cardiovascular physiology and pathophysiology. We 
also highlight some of the questions currently under active investigation 
regarding these extracellular membrane vesicles and their potential in 
diagnostic and therapeutic applications.