Our recent work on metal nanoparticles (Cu, Ni, Co) electrochemically deposited on an ultrathin polypyrrole film grown on a gold-coated silicon electrode shows that the morphology (size, shape, density and distribution) of these nanostructured materials can be easily controlled by varying the wet deposition conditions (pH, electrolyte concentration, deposition potential, charge, and current density), and the thickness and morphology of the polypyrrole film. Using similar electrochemical techniques, we have recently obtained mono-sized, uniformly distributed Fe core-shell nanoparticles with two different morphologies: quantum dots of 4-10 nm in diameter and 20x110 nm "nano-surfboards" (<5 nm thick). These nanoparticles are found to primarily consist of a Fe metallic core and a mixed Fe oxides shell (2-3 nm thick). In the present work, we report the first evidence of morphological changes induced by an external magnetic field during growth. Implications of constructing patterned nanostructured materials using this technique will also be discussed. @FootnoteText@ * Work supported by the Natural Sciences and Engineering Research Council of Canada.