Electron beam induced deposition is among the most prospective methods for size- and position-controllable nanofabrication of three-dimensional structures. Direct-write maskless nanostructure fabrication was performed with a scanning electron microscope. Three-dimensional iron structures were obtained by locally confined electron induced dissociation of an iron carbonyl (Fe(CO)(5)) precursor. Vertical nanopillars consisting of Fe with O and C contaminations were deposited. Two different growth regimes-electron induced growth and autonomous growth-were observed. The precursor pressure was shown to have a significant influence on the growth mode. (C) 2008 American Vacuum Society.