The simplicity of the experimental procedure and the structural similarity of [Fe30] to previously published molecules such as [Fe13,], [Fe17,] and [Fe34], and to bulk oxides such as ferrihydrite, which all possess structures composed of alternating layers of tetrahedral and octahedral Fe III ions, suggests that many more molecular iron oxides must exist. The self-assembly process also suggests that multifunctional 'core-shell' species in which the Fe-oxo core is encapsulated within another (stabilising) material, e.g. a polyoxometalate, will be attractive targets for a diverse array of applications.