Our biomimetic approach for fabricating organic-inorganic composites with structures similar to biominerals is based on a novel mineralization process, called the Polymer-Induced-Liquid-Precursor (PILP) process. This process enables the deposition of non-equilibrium mineral morphologies of calcite under low-temperature and aqueous-based conditions , including patterned thin films of calcite. We have recently found that when a surplus of acidic polymer is added, the patterned mineral films act as a secondary template for directing new crystal outgrowths, which form into complex morphologies of calcite with time, such as fibrous mats and “horsetails”. Two interdependent factors, the polymer and Ca-ion concentration, which change the local solution environment over time, appear to modulate the creation of these different structures. Such observations may provide clues for unraveling the long-standing mystery of how biological systems fabricate their sophisticated and complex morphologies.