Elemental abundance trends in the metal-rich thin and thick disks
  Thick disks are common in spiral and S0 galaxies and seem to be an inherent part of galaxy formation and evolution. Our own Milky Way is host to an old thick disk. The stars associated with this disk are enhanced in the alpha-elements as compared to similar stars present in the thin disk. The Milky Way thin disk also appears to be younger than the thick disk. Elemental abundance trends in stellar samples associated with the thin and the thick disks in the Milky Way are reviewed. Special attention is paid to how such samples are selected. Our current understanding of the elemental abundances and ages in the Milky Way thick and thin disks are summarised and discussed. The need for differential studies is stressed. Finally, formation scenarios for the thick disk are briefly discussed in the light of the current observational picture. 
S. Feltzing