Two-phase nanocomposite heteroepitaxial films with vertical microstructures hold great promise for various (multi)functional (e.g., multiferroic) electronic device applications. With the aim of creating addressable arrays, it is necessary to form spontaneously ordered structures over large areas. However, such structures have not, so far, been demonstrated. We have recently produced remarkable spontaneously ordered phase assemblies and find that these structures form concomitantly with 2-D vertical strain control, i.e., strain in the 2 phases is controlled along the vertical interface between them rather than being influenced by the substrate. In this paper, we report on our findings in the BiFeO3 and BaTiO3 ferroelectric systems.