  In this paper, we obtain the interior pointwise $C^{k,\alpha}$ ($k\geq 0$,
$0<\alpha<1$) regularity for weak solutions of elliptic and parabolic equations
in divergence form. The compactness method and perturbation technique are
employed. The pointwise regularity is proved in a very simple way and the
results are optimal. In addition, these pointwise regularity can be used to
characterize the structure of the nodal sets of solutions.
