paramagnetic, nuclear magnetic, and other res­ onance techniques-yield a large amount of information on the atomic, electronic, and real crystal structures. Crystal physics has also undergone vigorous development. Many re­ markable phenomena have been discovered in crystals and then found various practical applications. Other important factors promoting the development of crystallog­ raphy were the elaboration of the theory of crystal growth (which brought crystallography closer to thermodynamics and physical chem­ istry) and the development of the various methods of growing synthetic crystals dictated by practical needs. Man-made crystals became increas­ ingly important for physical investigations, and they rapidly invaded technology. The production . of synthetic crystals made a tremendous impact on the traditional branches: the mechanical treatment of mate­ rials, precision instrument making, and the jewelry industry.