ATLAS Commissioning with cosmic rays and first LHC beam

ATLAS is one of the four main experiments installed at LHC collider ring. The complexity of the detector requires a detailed and long commissioning phase that includes the integration of the sub-detectors into a single working system. During 2008, ATLAS commisioned with cosmic-rays the detector, the electronic components, the trigger system, the Data Acquisition read-out chain and the software systems. The intense commissioning work allowed to successfully record the first beam events of LHC during September 2008. We will present the status and results of the cosmic-ray based commissioning activities and of the preliminary results of the fist beam data analysis, with particular emphasis on the commissioning activities of TileCal, the barrel hadronic calorimeter of ATLAS experiment.