Aging phenomena characterize the non-equilibrium dynamics of many disordered and complex systems (glassess, amorphous polymers, etc). Nevertheless, similar behaviors are also observed in much simpler cases such as pure ferromagnets quenched at their critical points, where the emerging universality allows a quite detailed investigation of several aspects of the non-equilibrium dynamics. The talk focusses on the field-theoretical approach as a viable tool to study the aging behavior and the persistence properties of the Ising model.