From the reflection and reverberation of X-rays off the innermost regions of AGN accretion discs, a three-dimensional picture is starting to emerge of the extreme environments around supermassive black holes in which intense X-ray emission is produced and jets are launched at close to the speed of light.

Recent advances in the analysis of the X-ray emission and its variability in AGN, observed by the great X-ray observatories, coupled with general relativistic ray tracing simulations, have revealed vast amounts of information about the extreme environments in the immediate vicinity of the black hole event horizon. The effects of general relativity on the reflected emission can be exploited to pinpoint the location of reflection in the strong gravitational field, while time delays in the X-ray echoes off the accretion disc enable the structure of the innermost regions to be mapped.

We discover how the X-ray emitting corona evolves on long and short timescales, giving rise to orders of magnitude variation in luminosity as well as the processes the corona can undergo during transient events, most notably the collimation and ejection of portions of the corona during X-ray flares, reminiscent of the aborted launching of a jet. The latest X-ray reverberation studies are revealing, for the first time, structure within the corona including a persistent collimated core akin to the base of a jet, even in radio-quiet sources, alongside a second component associated with the accretion disc itself.

This gives us important insight into the small-scale processes close to the event horizon that enable supermassive black holes to power some of the most luminous objects in the Universe, launch vast jets and play their important role in the formation of structure in the Universe.