The use of cosmic abundances to constrain the galaxy formation process offers an important complementary approach to the current simulations of galaxy formation. In particular, our Galaxy and the Local Group galaxies turned out to be the ideal test-ground for the theories of galaxy formation because resolved in individual stars. The new information provided by high-resolution spectra of stars in the halo, bulge, thick and thin disks of the Milky Way will be discussed, with particular emphasis on its link to the big picture of galaxy formation and cosmology. Particular attention will be paid on the most-metal poor halo stars which constitute important fossil records of the nature of the first stellar generations to enrich the Universe. I will show that we have strong reasons to believe the first generation of stars to have been radically different than their present day counterparts.