  The electromagnetic polarizabilities are fundamental properties of the proton
that characterize its response to an external EM field. The generalization of
the EM polarizabilities to non-zero four-momentum transfer opens up a powerful
path to study the internal structure of the proton. They map out the spatial
distribution of the polarization densities in the proton, provide access to key
dynamical mechanisms that contribute to the electric and the magnetic
polarizability effects, and allow to determine fundamental characteristics of
the system, such as the electric and the magnetic polarizability radii. This
article reviews the knowledge of the proton EM generalized polarizabilities. An
introduction is given to the basic concepts and to the theoretical framework,
that is then followed by a discussion that emphasizes the recent developments
and findings of the Virtual Compton scattering experiments and future
perspectives on the topic.
