Early in this century, the newly discovered x-ray diffraction by
crystals made a complete change in crystallography and in the whole
science of the atomic structure of matter, thus giving a new impetus to
the development of solid-state physics. Crystallographic methods, pri-
marily x-ray diffraction analysis, penetrated into materials sciences,
mol- ecular physics, and chemistry, and also into many other branches of
science. Later, electron and neutron diffraction structure analyses be-
came important since they not only complement x-ray data, but also
supply new information on the atomic and the real structure of crystals.
Electron microscopy and other modern methods of investigating mat-
ter-optical, electronic 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.