An alternative route for producing L1(0) FePt nanoparticles based on the self-organization of diblock copolymers into spherical micelles is presented. it overcomes all of the drawbacks of current colloidal strategies towards densely packed arrays of ferromagnetic FePt nanoparticles while still guaranteeing areal densities exceeding 1 Tbits inch(-2). The figure shows a sketch of the metal-salt-loaded micelles deposited on a substrate: a polystyrene shell (red) covers the poly (2-vinylpyridine) core (blue) forming a nanoreactor loaded with metal salt (yellow).