​his article describes the fabrication of nanosized magneto-vesicles (MVs) comprising tunable layers of densely packed superparamagnetic iron oxide nanoparticles (SPIONs) in membranes via cooperative assembly of polymer-tethered SPIONs and free poly(styrene)-b-poly(acrylic acid) (PS-b-PAA).  The membrane thickness of MVs could be well controlled from 9.8 to 93.2 nm by varying the wt. ratio of PS-b-PAA to SPIONs.​