  Variability studies hold information on otherwise unresolvable regions in
Active Galactic Nuclei (AGN). Population studies of large samples likewise have
been very productive for our understanding of AGN. These two themes are coming
together in the idea of systematic variability studies of large samples - with
SDSS, PanSTARRS, and soon, LSST. I summarise what we have learned about the
optical and UV variability of AGN, and what it tells us about accretion discs
and the BLR. The most exciting recent results have focused on rare large-scale
outbursts and collapses - Tidal Disruption Events, changing-look AGN, and large
amplitude microlensing. All of these promise to give us new insight into AGN
physics.
