Stellar clusters are important tracers of the properties of the Milky Way
and are fundamental to understand its formation and evolution mechanisms.
Recently, we have begun to see globular clusters as complex objects,
probably with several episodes of star formation, while open clusters
still appear to be truly simple stellar populations. This has been
possible thanks to extensive studies with high resolution spectroscopy. I
will describe results obtained on globular clusters by our "small" FLAMES
survey, which has been crucial to establish the multiple population
framework for GCs. I will then move to the first results on open clusters
obtained by the Gaia-ESO Survey. In both cases the legacy value of these
data and studies will be presented.