  Gaia DR3 opens a new era of all-sky spectral analysis of stellar populations
thanks to the nearly 5.6 million stars observed by the RVS and parametrised by
the GSP-spec module. The all-sky Gaia chemical cartography allows a powerful
and precise chemo-dynamical view of the Milky Way with unprecedented spatial
coverage and statistical robustness. First, it reveals the strong vertical
symmetry of the Galaxy and the flared structure of the disc. Second, the
observed kinematic disturbances of the disc -- seen as phase space correlations
-- and kinematic or orbital substructures are associated with chemical patterns
that favour stars with enhanced metallicities and lower [alpha/Fe] abundance
ratios compared to the median values in the radial distributions. This is
detected both for young objects that trace the spiral arms and older
populations. Several alpha, iron-peak elements and at least one heavy element
trace the thin and thick disc properties in the solar cylinder. Third, young
disc stars show a recent chemical impoverishment in several elements. Fourth,
the largest chemo-dynamical sample of open clusters analysed so far shows a
steepening of the radial metallicity gradient with age, which is also observed
in the young field population. Finally, the Gaia chemical data have the
required coverage and precision to unveil galaxy accretion debris and heated
disc stars on halo orbits through their [alpha/Fe] ratio, and to allow the
study of the chemo-dynamical properties of globular clusters. Gaia DR3
chemo-dynamical diagnostics open new horizons before the era of ground-based
wide-field spectroscopic surveys. They unveil a complex Milky Way that is the
outcome of an eventful evolution, shaping it to the present day (abridged).
