Thin films of cubic BaTiO3 were processed hydrothermally at 40 degrees-80 degrees C by reacting thin layers of titanium organometallic liquid precursors in aqueous solutions of either Ba(OH)(2) or a mixture of NaOH and BaCl2. All films (thickness similar to 1 mu m) were polycrystalline with grain sizes ranging from nano- to micrometer dimensions, BaTiO2 formation was facilitated by increasing [OH-], [Ba2+], and the temperature, The film structure was related to the nucleation and growth behavior of the BaTiO3 particles, Films processed at relatively low [OH-], [Ba2+], and temperatures were coarse grain and opaque, but increasing [OH-], [Ba2+], and temperature caused the grain size to decrease, resulting in transparent films.