  How can we gain a detailed insight into the hydrodynamic response of the
system created in heavy ion collisions to the fluctuating initial geometry and
viscous effects? Do we create a strongly interacting medium in proton-nucleus
and proton-proton collisions, or rather a system of partons undergoing few
scatterings? To what extent can we discriminate between initial momentum
correlations and flow generated as a response to the initial geometry via
interactions in the final state? Do measurements of identified particle flow
confirm the observations from inclusive charged hadrons? An experimental
overview of anisotropic flow measurements, ranging from large down to the
smallest collision systems, is given in these proceedings.
