Azimuthal Angle correlations in Large and Small Systems ­ - Why the fuss?

In this talk, I will discuss recent momentum anisotropy measurements for a broad range of systems at both RHIC and LHC energies. In particular, the respective roles of final state effects versus initial state momentum domain effects in explanations of the measurements, will be addressed. I will also discuss how these measurements can be leveraged to constrain the properties of the medium produced in these collisions.