In this survey we review positive inverse spectral and inverse resonant
results for the following kinds of problems: Laplacians on bounded domains,
Laplace-Beltrami operators on compact manifolds, Schr\"odinger operators,
Laplacians on exterior domains, and Laplacians on manifolds which are
hyperbolic near infinity.
We use the Dong-Sogge-Zelditch formula to obtain a lower bound for the volume
of the nodal sets of eigenfunctions. Our result improves the recent results of
Sogge-Zelditch and in dimension 3 gives a new proof for a recent result of
Colding-Minicozzi.