  The Chapter is devoted to reviewing the main features of aging in non
disordered systems relaxing via domain growth, after an istantaneous
temperature quench. Using the autocorrelation and autoresponse functions to
gauge the deviation from equilibrium, an hierarchy of processes is obtained by
changing the temperature of the quench and the space dimensionality. The
special role of the lower critical dimensionality is highlighted. Basic
properties like the separation of the time scales and the splitting of degrees
of freedom into fast and slow variables are treated in detail, both in general
terms and through analytical calculations in solvable models. Though domain
growth is believed to be a well understood paradigma of slow relaxation,
emphasis of this review is on the non trivial aspects, not yet fully clarified,
like the response function scaling behavior.
