Abstract: The observation of the highest-energy cosmic photons by the Large High Altitude Air Shower Observatory (LHAASO) has opened a new era of ultra-high energy gamma-ray astronomy. The whole process of gamma-ray burst GRB 221009A was observed, including the first detection of photons with energies around or above 10 TeV. I briefly review these discoveries and show that they not only play an important role in understanding the origin of cosmic rays, but also can be used for testing the basic assumptions of Lorentz invariance and constant light speed in relativity, and for exploring new physics beyond the standard model.