The production of prompt photons in association with jets in proton-proton collisions at the LHC provides a testing ground for perturbative QCD (pQCD) with a hard colourless probe less affected by hadronisation effects than jet production. The measurements of the angular correlations between the photon and the jets can be used to probe the dynamics of the hard-scattering process. We present here the latest ATLAS cross-section measurement of isolated photon plus jet at $\sqrt{s}=13$ TeV, differential in a wide range of kinematic variables describing the photon plus jet production dynamic. We will also present for the first time ATLAS measurements on the differential cross sections of isolated-photon plus heavy-flavour jet production at $\sqrt{s}=8$ TeV. The results are compared to recent theoretical predictions.