The Milky Way thin disk structure as revealed by stars and young open
  clusters
  In this contribution I shall focus on the structure of the Galactic thin
disk. The evolution of the thin disk and its chemical properties have been
discussed in detail by T. Bensby's contribution in conjunction with the
properties of the Galactic thick disk, and by L.Olivia in conjunction with the
properties of the Galactic bulge. I will review and discuss the status of our
understanding of three major topics, which have been the subject of intense
research nowadays, after long years of silence: (1) the spiral structure of the
Milky Way, (2) the size of the Galactic disk, and (3) the nature of the Local
arm (Orion spur), where the Sun is immersed. The provisional conclusions of
this discussion are that : (1) we still have quite a poor knowledge of the
Milky Way spiral structure, and the main dis-agreements among various tracers
are still to be settled; (2) the Galactic disk does clearly \textit{not} have
an obvious luminous cut-off at about 14 kpc from the Galactic center, and next
generation Galactic models need to be updated in this respect, and (3) the
Local arm is most probably an inter-arm structure, similar to what we see in
several external spirals, like M~74. Finally, the impact of GAIA and LAMOST in
this field will be briefly discussed as well.
