Observation of long rang azimuthal correlation in small collision systems (p+p/A) has triggered an enormous excitement in the heavy-ion community. However, it is presently unclear to what extent the experimentally observed correlations should be attributed to initial state momentum correlations and/or the final state response to the initial state geometry. Based on a short introduction, I will discuss how initial state momentum correlations emerge naturally in high-energy scattering processes and address the question to what extent collective features can be described from an initial state perspective. By further matching the initial state in p+Pb collisions to a partonic transport model, I will also present first results to quantify the relative importance of initial state and final state effects as a function of the event multiplicity.