  Ultrafast optical pulses are an increasingly important tool for controlling
quantum materials and triggering novel photo-induced phase transitions.
Understanding these dynamic phenomena requires a probe sensitive to spin,
charge, and orbital degrees of freedom. Time-resolved resonant inelastic X-ray
scattering (trRIXS) is an emerging spectroscopic method, which responds to this
need by providing unprecedented access to the finite-momentum fluctuation
spectrum of photoexcited solids. In this Perspective, we briefly review
state-of-the-art trRIXS experiments on condensed matter systems, as well as
recent theoretical advances. We then describe future research opportunities in
the context of light control of quantum matter.
