The observation of gamma-ray sources at energies between tens of GeV and tens of TeV has been driven by ground-based Cherenkov telescopes. The observational techniques and methods employed have been continuously refined in the past years and have lead to the discovery of a steadily growing number of sources and source types. Similar to other branches of observational Astrophysics in the past, the field undergoes currently a transition from a discovery-driven to an exploration-driven stage. In this context, recent developments are summarized and highlights are presented.