ATLAS is a particle physics experiment at the Large Hadron Collider (LHC) at CERN which is the world’s highest energy proton-proton collider presently running. LHC begins operation in 2009 at the center of mass energy of 900 GeV and 2.36 GeV and since then has delivered p-p collisions at 7, 8 and 13 TeV. The ATLAS detector is searching for new discoveries in the head-on collisions of protons of extraordinarily high energy and will increase our knowledge of the basic forces that have shaped our universe since the beginning of time. It has already discovered the source of electroweak symmetry breaking (the Higgs boson) in 2012 and it has searched for new forms of matter such as supersymmetric states, putting limits on their masses. The group of INFN-Roma Tor Vergata has contributed to the construction of the RPC trigger chambers and to the front-end electronics of the ATLAS muon system. The INFN-Roma Tor Vergata group has developed expertise and is working on top quark physics, bottom, charm, and Higgs boson physics and searches for deviations from the Standard Model.