The birth of ground-based gamma-ray astronomy is a success story. In the first half of the 2000s, thanks to the Imaging Cherenkov Telescope systems, the field developed into a real astronomical discipline with more than three hundred VHE (or TeV) gamma-ray emitters representing more than a dozen astronomical source populations. Today, we are witnessing a second revolution in the field - this time in the UHE or PeV range. To the great surprise of the community, dozens of objects turned out to emit gamma rays with energy spectra extending well beyond 100 TeV. In this talk, I will discuss the reasons for this great success, the implications of the recent results, and the anticipated future.