  The last decade has seen a significant gain in both space and ground-based
monitoring capabilities, producing vastly better coverage of BH X-ray binaries
during their (rare) transient events. This interval included two of the three
brightest X-ray outbursts ever observed, namely V404 Cyg in 2015, and MAXI
J1820+070 in 2018, as well as the outburst of Swift J1357.2-0933, the first
such system to show variable period optical dipping. There are now superb
multi-wavelength archives of these outbursts, both photometric and
spectroscopic, that show substantial outflows in the form of jets and disc
winds, and X-ray spectroscopy/timing that reveals how the inner accretion disc
evolves. The ground-based AAVSO optical monitoring of the MAXI J1820+070 event
was the most extensive ever obtained, revealing periodic variations that
evolved as it approached its state transition. These modulations were of an
amplitude never seen before, and suggested the development of an
irradiation-driven disc warp that persisted through the transition. All these
results have demonstrated the power of extensive multi-wavelength photometric
and spectroscopic monitoring on all time-scales.
