  We review the recent baryon chiral perturbation theory results for the
nucleon polarisabilities that describe the different regimes of nucleon Compton
scattering --- real, virtual, and doubly virtual. We stress the importance of
the empirical verification of the theory in the context of the calculation of
the inelastic nucleon structure corrections, such as the two-photon exchange
contributions. We also discuss the recently obtained constraints that relate
the different regimes of nucleon Compton scattering and can provide additional
information on the nucleon structure.
