  The presence of correlations between particles significantly separated in
pseudorapidity in proton-proton and proton-nucleus collisions revealed
surprises in the early LHC data. Are the physical processes responsible for the
observed long-range pseudorapidity correlations and their azimuthal structure
the same in small collision systems as in heavy ion collisions? Whereas in the
case of heavy ion collisions "flow" is interpreted as generated by initial
geometric inhomogeneities, calculations indicate that initial-state momentum
correlations are present and could contribute to the observed azimuthal
anisotropy in small systems. Probes involving heavy quarks provide us with a
unique opportunity to disentangle different quantum chromodynamics effects at
the boundary between low- and high-$p_{\mathrm{T}}$ interactions, and hence
shed light on the origin of flow in small collision systems. A selection of the
latest measurements is presented for the flow and production of heavy flavor
hadrons and their decay products.
