In this paper, shape-controlled crystallization and self-assembly of CaCO 3 hierarchical architectures has been successfully synthesized via the gas diffusion method in egg white solution. Stepwise growth and assembly of CaCO 3 nanoparticles has been observed from transition of an amorphous CaCO 3 to the crystallization and stabilization of platelet-like nanoparticles and eventually, the wool sphere-like CaCO 3 hierarchical architectures assembling of nanoparticles. The proteins binding on nanoparticle surfaces proved to regulate the growth of nanoparticles and subsequent assembly into hierarchical superstructures via electrostatic and dipole interactions. The samples were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and nano mechanical Tester. The measured average elastic modulus and the hardness of calcium carbonate hybrid materials were 5.32GPa and 0.1886GPa by the nano-indenter test, respectively.