Slow-light polaritons are quasi-particles generated in the interaction of light with laser-driven atoms under conditions of electromagnetically induced transparency (EIT). Their dispersion can be controlled to a large extend, representing massive Schroedinger particles on the one hand or multi-component, i.e. spinor objects with
a Dirac-like spectrum on the other. In the latter case characteristic length and energy scales can be widely tuned, making relativistic effects accessible in the lab. Making use of the tunability of the mass the delocalization transition of the random-mass Dirac model with off-diagonal disorder can be observed. Combining EIT with Rydberg atoms provides strong interactions between polaritons, giving rize to interesting many-body phenomena, such as "hard sphere" photons, crystallization or bosonic quantum Hall effects. I will argue that recent experiments on EIT in Rydberg gases have already given evidence for the formation of "hard sphere" photons.