Kern's inequalities have played a central role in the development of l
inear elasticity, not only in connection with the basic theoretical is
sues such as existence and uniqueness, but also in a variety of applic
ations. The Korn inequalities, and other related inequalities for inte
grals of quadratic functionals, also arise in the analysis of viscous
incompressible fluid flow. The dimensionless optimal constants appeari
ng in these inequalities, the Kern constants, depend only on the shape
of the domains of concern. Information on the geometric dependence of
these constants is essential in applications. In this review article,
we summarize the major results on Korn's inequalities for bounded dom
ains in two and three dimensions, with emphasis on results concerning
the Korn constants. Some applications in continuum mechanics are also
described.