  We present asymptotic giant branch (AGB) models of solar metallicity, to
allow the interpretation of observations of Galactic AGB stars, whose distances
should be soon available after the first release of the Gaia catalogue. We find
an abrupt change in the AGB physical and chemical properties, occurring at the
threshold mass to ignite hot bottom burning,i.e. $3.5M_{\odot}$. Stars with
mass below $3.5 M_{\odot}$ reach the C-star stage and eject into the
interstellar medium gas enriched in carbon , nitrogen and $^{17}O$. The higher
mass counterparts evolve at large luminosities, between $3\times 10^4
L_{\odot}$ and $10^5 L_{\odot}$. The mass expelled from the massive AGB stars
shows the imprinting of proton-capture nucleosynthesis, with considerable
production of nitrogen and sodium and destruction of $^{12}C$ and $^{18}O$. The
comparison with the most recent results from other research groups are
discussed, to evaluate the robustness of the present findings. Finally, we
compare the models with recent observations of galactic AGB stars, outlining
the possibility offered by Gaia to shed new light on the evolution properties
of this class of objects.
