While recent sky surveys have uncovered large numbers of ever fainter
Milky Way satellites, their classification as star clusters, low-luminosity
galaxies, or tidal overdensities remains often unclear. Likewise, their
contributions to the build-up of the halo is yet debated.
In this talk I will discuss the current knowledge of the stellar populations
and chemo-dynamics in these puzzling satellites, with a particular focus on
some peculiar chemical abundance ratios some dwarf spheroidal galaxies and
globular clusters, out to the outskirts of the Galactic halo, which also hold
further clues to the contribution of these systems to the halo assembly.