Abstract: The compact muon solenoid detector is one of the four experiments on the Large Hadron Collider at CERN. It was conceived to study proton-proton collisions at a centre-of-mass energy of 14 TeV and at luminosities up to 1034 cm-2s-1. The detector is characterized by its high ompactness, with the muon chamber encompassing almost the entire 4π solid angle. A high-field superconducting solenoid surrounds a silicon tracker, an electromagnetic calorimeter, and a hadron calorimeter. The resolution is excellent for detecting processes which involve electrons, photons and especially muons in the final state.