  This review gives an update on virtual Compton scattering (VCS) off the
nucleon, $\gamma^* N \to N \gamma$, in the low-energy regime. We recall the
theoretical formalism related to the generalized polarizabilities (GPs) and
model predictions for these observables. We present the GP extraction methods
that are used in the experiments: the approach based on the low-energy theorem
for VCS and the formalism of Dispersion Relations. We then review the
experimental results, with a focus on the progress brought by recent
experimental data on proton generalized polarizabilities, and we conclude by
some perspectives in the field of VCS at low energy.
