Our understanding of the demographics and evolution of supermassive black holes (SMBHs) beyond the local universe is limited to actively growing SMBHs, where relatively stable accretion of gas persists over several hundreds of millions of years.

A growing number of transient phenomena in galaxy nuclei have recently begun to shed new light on SMBH demographics and the physics of gas accretion onto these objects, tracing events where this accretion has drastically intensified or diminished.

I will review some of these new classes of highly variable phenomena, focusing on new results obtained with fast, multi-wavelength follow-up observations. These include “changing look AGN”, and other, yet poorly understood UV-bright flares from accreting SMBHs. While these events observationally differ from the tidal disruption events known to date, the physics behind them may be interlinked. I will also mention how new surveys will discover many more transients from SMBHs that will allow us to better understand the ways in which SMBHs turn their accretion “on” and “off”.