PbSe nanorods and branched nanorods are grown using binary Au-Fe3O4 nanoparticles as seeds. PbSe nucleates on the gold portion of the seed particle and grows anisotropically as one or more straight or branched nanorods. Seeding with binary particles has significant advantages over seeding with pure-metal particles. The top TEM images show the different growth morphologies obtained by varying seed-to-precursor ratios and the bottom images show PbSe nanorods and branched nanocrystals (see also inside front cover).