Canadian and American researchers have discovered a new mechanism by which membrane vesicles are made. These self-contained nanoparticles trap proteins, RNA and other molecules from inside or outside of living cells as nutrients or regulate the numbers of cell surface hormone receptors, such as those for insulin, to control the sensitivity of cells to hormones. They also deliver protein hormones to the surface of cells where they are released into the surroundings to act on cells at a distance. These processes are essential to the normal function of our cells and disfunctions are implicated in several diseases, including cancers, heart disease and neuropsychiatric disorders. Finally, it is the mechanism by which nanoparticles encapsulating mRNA vaccines are taken up into cells.