Air-stable Fe magnetic nanoparticles entrapped within carbon and porous crosslinked polystyrene microspheres of narrow size distribution were prepared by the following sequential steps: (1) Polystyrene/poly(divinyl benzene) and polystyrene/poly(styrene-divinyl benzene) uniform micrometer-sized composite particles were prepared by a single-step swelling of uniform polystyrene template microspheres dispersed in an aqueous continuous phase with emulsion droplets of dibutyl phthalate containing the monomers divinyl benzene and styrene and the initiator benzoyl peroxide. The monomers within the swollen polystyrene template microspheres were then polymerized by raising the temperature to 73 degrees C; (2) Porous poly (divinyl benzene) and poly(styrene-divinyl benzene) uniform crosslinked microspheres were prepared by dissolution of the polystyrene template part of the former composite particles; (3) Uniform magnetic poly(divinyl benzene)/Fe and poly(styrene-divinyl benzene)/Fe composite microspheres were prepared by entrapping Fe(CO)(5) within the porous crosslinked microspheres, by suction of the Fe complex into the dried porous particles, followed by decomposition of the encapsulated Fe(CO)(5) at 200 degrees C in Ar atmosphere; (4) Uniform magnetic air-stable C/Fe composite microspheres were prepared similarly, apart from changing the decomposition temperature from 200 to 600 degrees C. (c) 2007 Wiley Periodicals, Inc.