Oriented inorganic films can be grown under Langmuir monolayers floating on supersaturated aqueous solutions. This process mimics biomineralization, and is potentially an easy method for growing designed inorganic films. Grazing-incidence X-ray diffraction (in situ) and scanning electron microscopy (of films transferred to substrates) reveal that oriented growth occurs via two distinct mechanisms. First, there can be epitaxial growth, with organic and inorganic lattices relaxing to allow an exact match. A variant is the appearance of a reconstructed surface superlattice that mediates between the unstrained organic and bulk inorganic structures. Second, the alignment of crystals already formed can be enhanced via spontaneous self-aggregation into oriented chains. (c) 2006 Elsevier B.V. All rights reserved.