The crystal defects of the nano-scale, which are called artificial pinning centers (APCs), were successfully introduced into high-temperature superconductors (HTS) by nanotechnology, in order to strongly pin the quantized vortices. Critical current densities Jc of the HTS films were dramatically improved by APCs whose dimensions were controlled. By this method, the in-field Jc (77 K) of the high-quality, epitaxial films was improved by one order of magnitude or more compared with the values of the past. A current outline of the research is described in this paper.