Operation and performance of the CMS Electromagnetic Calorimeter during the 2010 run

The operation and performance of the CMS electromagnetic calorimeter (ECAL) during the 2010 run at the LHC, with pp collisions at ?s =7 TeV will be reviewed. Pure samples of electrons and photons, mainly coming from decays of known resonances, have been exploited to improve and verify the detector calibration and stability, the reconstruction algorithms and the particle identification efficiency and purity. A thorough review of all these aspects will be given, with particular emphasis on the calibration procedures.