Tomography of a cell with multiple lipid vesicles transported to the cell surface. Credit: UPF/Sasha Meek An international group of researchers led by Pompeu Fabra University has discovered the nanomachine that controls constitutive exocytosis: the uninterrupted delivery of spherical molecular packages to the cell surface. This is an essential activity present in virtually all organisms to preserve cell fitness and other vital functions such as communicati