  Frequency combs can be generated in millimeter-sized optical resonators
thanks to their ability to store extremely high light intensities and the
nonlinearity of their materials. New frequencies are generated through a
cascaded parametric amplification process which can result in various optical
waveforms, from ultrastable pulse patterns to optical chaos. These Kerr
frequency combs have been studied extensively, with a wealth of fascinating
nonlinear dynamics reported, and myriads of applications being developed,
ranging from precision spectroscopy and Lidars to telecom channel generators.
