New observations of gamma-rays in 100 TeV energy domain by HAWC and LHAASO, with future follow up by CTA, open new possibilities for understanding of particle acceleration to extreme energies in astronomical sources in our Milky Way galaxy. These sources, dubbed “PeVatrons” (yet to be identified) produce particles with energies up to several Peta-electronVolt, three orders of magnitude higher than those attained in the most powerful human-made accelerator LHC. They can also be responsible for the astrophysical neutrino signal observed by IceCube neutrino telescope.