  We review studies on spin-dependent tunneling phenomena in systems containing
ferromagnetic nanoparticles. We discuss preparation methods of assembling
nanoparticles as well as the mechanisms and results of spin-dependent transport
properties. The emphasis of this review is on characteristic spin-dependent
tunneling phenomena such as enhanced tunnel magnetoresistance (TMR) due to
co-tunneling in the Coulomb blockade regime and sign changes of the TMR due to
spin accumulation in nanoparticles.
