  The origin of dwarf spheroidal galaxies (dSphs) is investigated in a global
cosmological context by simultaneously following the evolution of the Milky Way
Galaxy and its dwarf satellites. This approach enable to study the formation of
dSphs in their proper birth environment and to reconstruct their own merging
histories. The proposed picture simultaneously accounts for several dSph and
Milky Way properties, including the Metallicity Distribution Functions of
metal-poor stars. The observed features are interpreted in terms of physical
processes acting at high redshifts.
