  We discuss geometrical scaling (GS) for the prompt (direct) photons produced
in heavy ion collisions. To this end we first introduce the concept of GS and
illustrate its emergence on the example of charged particles. Next, we analyse
direct photon data from RHIC and from the LHC. We show that the data support
the hypothesis of GS in terms of participant number related to different
centrality classes. We also study GS at different energies, however a more
detailed study will be possible only when data for at least three different
energies from one experiment will be available and also when we use the data
obtained from the collisions of large systems (Cu+Cu, Au+Au, Pb+Pb) and small
systems (p+p, d+Au, p+Au).
