Over the past decades high energy heavy ion collisions at the Relativistic Heavy Ion Collider and the Large Hadron Collider produced and immense amount of information about the matter at unprecedented extremes of energy and density. Experiments observed signatures of a strongly coupled Quark Gluon Plasma (QGP) - a thermalised state in which quarks and gluons are the system’s relevant degrees of freedom.

Among the experiments operating at the LHC, results from the ATLAS experiment with Pb+Pb collisions have furthered our knowledge about the QGP as we work towards a deeper understanding of the nature of quark and gluon interactions. In addition to the Pb+Pb collisions, ATLAS has also studied p+Pb collisions in which unexpected collective properties have been observed. Recent results from Pb+Pb and p+Pb collisions will be discussed in the talk.