Silica nanospheres with varied morphologies and pore structures, including mesoporous nanospheres, nanospheres with hierarchical pores (from 2 to 100 nm), and hollow nanospheres of mesoporous shell, were fabricated at room temperature simply by regulating the ethanol/ethyl ether volume ratio in the starting solution. The silica nanostructures were characterized by small-angle X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption measurements. Based on experimental results, a plausible mechanism for the structural regulation of mesoporous silicas has been put forward. These novel nanostructures of hierarchical pores provide an ideal scaffold for biological, medical, and catalytic applications.