Contribution invited talk
On the smallest droplets of QCD fluids
Hydrodynamics is the accepted framework to describe the evolution of systems created in relativistic heavy-ion collisions. In smaller collision systems, such as proton-lead and proton-proton collisions, other, non-hydrodynamic explanations for the experimentally observed flow signals have been suggested. So which explanation is right or are they both? In this talk I review the applicability of hydrodynamics to small systems, and the conclusions one can draw for the origin of experimental flow signals in small collision systems.