Optical Kerr microresonators in the last years have acquired attention from the scientific community, being from a fundamental point of view rich complex physical systems but at the same time, thanks to the late improvements of the nanofabrication technologies, feasible to fabricate in a controlled way. That has recently resulted in a plethora of cutting-edge applications spanning from spectroscopy to LIDAR and atomic clocks. The complex behaviour of the optical field within the resonator arises from being both an out-of-equilibrium and nonlinear system, leading to the emergence of bistability, hysteresis of the optical resonance, chaotic behaviour, and self-organization in coherent states.