  We review some of the recent developments regarding mass, angular momentum
and pressure forces inside hadrons. These properties are all encoded in the
energy-momentum tensor of the system, which is described at the
non-perturbative level in terms of gravitational form factors. Similarly to
electromagnetic form factors, Fourier transforms of gravitational form factors
allow one to map out the distribution of the above mechanical properties in
position space, providing a whole new way of studying in detail the internal
structure of hadrons.
