Low-metallicity (sub-SMC) massive stars
  The double distance and metallicity frontier marked by the SMC has been
finally broken with the aid of powerful multi-object spectrographs installed at
8-10m class telescopes. VLT, GTC and Keck have enabled studies of massive stars
in dwarf irregular galaxies of the Local Group with poorer metal content than
the SMC. The community is working to test the predictions of evolutionary
models in the low-metallicity regime, set the new standard for the metal-poor
high-redshift Universe, and test the extrapolation of the physics of massive
stars to environments of decreasing metallicity. In this paper, we review
current knowledge on this topic.
