Super star clusters as probes of massive star evolution and the IMF at   extreme metallicities
  Young super star clusters and young compact massive star forming regions can provide useful information on their burst properties (age, burst duration, SFR), the upper end of the IMF and yield new constraints on the evolution of massive stars. Through the study of their stellar populations we can in particular extend our knowledge on massive stars to extreme metallicities unavailable for such stars in the Local Group.   Here we summarise the main results from recent studies on two metallicity extremes: Wolf-Rayet and O star populations in very metal-poor BCD, and metal-rich compact nuclear SF regions. 
Daniel Schaerer (OMP, Toulouse), Natalia G. Guseva, Yuri I. Izotov   (Main Astronomical Observatory, Kiev)