In this talk I will present recent theoretical and experimental work in nonequilibrium interacting light-matter systems realized in the circuit-QED architecture. The first example is the experimental observation of a dissipation-driven localization transition in a strongly interacting open photonic system. This experiment also demonstrates a small-scale realization of a new class of quantum simulator, whose well-controlled coherent and dissipative dynamics is suited to the study of quantum many-body phenomena out of equilibrium. par As a second example of strongly interacting photons, I present recent work on a new regime of light-matter interactions, multimode strong coupling (MMSC), where the coupling is comparable to the free spectral range of the cavity and the rate at which a qubit can absorb a photon from the cavity is comparable to the round trip transit rate of a photon in the cavity. Our results capture complex multimode, multi photon processes, where we observe remarkably widespread and structured resonance fluorescence, whose origin extends beyond cavity enhancement of sidebands, and the emergence of ultranarrow linewidths. Beyond the novel phenomena presented here, MMSC opens a major new direction in the exploration of light-matter interactions. par I will close with some ongoing and future work on the study of phase transitions in driven dissipative. An intriguing question in the physics of interacting many-body systems, when they are coupled to an environment and externally driven into a steady state, is whether there exist new universality classes going beyond the standard classification that has been developed for dynamical critical phenomena in equilibrium.