The scientific study of crystals. In 1912, it
was found that the shape and size of the unit
cell of a crystal can be discovered by
X-rays, thus opening up an entirely new way
of `seeing' atoms. This means of determining
the atomic patterns in a crystal is known as
X-ray diffraction. It has been shown that
even purified biomolecules, such as proteins
and DNA, can form crystals, and such
compounds may now be studied by the same
method. Another field of application of X-ray
analysis lies in the study of metals and
alloys. Crystallography is also of use to the
geologist studying rocks and soils. Many
materials were not even suspected of being
crystals until they were examined by X-ray
crystallography. By this method it has been
found that many substances have unit cells or
boxes which are exact cubes, for example
ordinary table salt (sodium chloride).