Astronomical observations through the new 100 TeV gamma-ray observational window by HAWC, Tibet and LHAASO air shower arrays, and, in the near future, by the Cherenkov Telescope Array CTA open a range of completely new possibilities for the study of highest energy galactic cosmic ray sources. These sources, dubbed "PeVatrons" (yet to be identified) produce particles with energies in excess of Peta-electronVolt, three orders of magnitude higher than those attained in the most powerful human-made accelerator LHC.