(Figure Presented) Spotty iron: Surface deposition of holo human transferrin from aqueous solutions gives rise to long protein fibrils with regular periodic nanomineralization along their length of an FeIII oxide/hydroxide closely resembling lepidocrocite (γ-FeO(OH)). Such a new role for this serum protein could have important biological and medical implications. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.