Terahertz technology (frequencies ranging from 100 GHz to 30 THz) has now received more and more attentions due to its wide applications in various scientific and technical fields. Because of their capability to prohibit the propagation of terahertz irradiation for all directions in their band gaps, three dimensional terahertz photonic crystals (3D-TPCs) with a periodic diamond structure could create specific functionalities. The direct-writing technology had been adopted to create complex 3D-TPCs with various material systems. However, these 3D-TPCs had certain terahertz responses because their composition and structures were fixed after their creation. In this invited presentation, I will talk about our recent work on the development of creation of 3D-TPCs by the direct-writing technology with tunable terahertz properties by structure, composition, and various external stimulations. Novel functions could be integrated to these 3D-TPCs for cutting-edge terahertz technology and other relative technological applications.