This chapter begins with an explanation of the similarity of electronic waves to light waves, which is useful to understand the behavior of electron wavefunctions. It presents examples of tailored materials with atomic/molecular assembling by scanning tunneling microscopy, molecular beam epitaxy (MBE), plasma chemical vapor deposition (CVD), atomic layer deposition, sputtering, and vacuum deposition polymerization. D. M. Eigler and E. K. Schweizer developed an atomic manipulation process that enables atoms to slide across a surface to definite positions. Vacuum deposition polymerization is a method for polymer film deposition in vacuum using vacuum evaporation. Vacuum deposition polymerization is regarded as CVD for polymer film fabrication. MBE is an important growth technique for inorganic thin films on flat substrate surfaces. One of the functional devices fabricated by MBE is the high-electron-mobility transistor, which is basically a field-effect transistor. Another functional device is the light modulator, which consists of multiple quantum wellsthat can be fabricated by MBE.