  Broad emission lines, particularly broad iron-K lines, are now commonly seen
in the X-ray spectra of luminous AGN and Galactic black hole binaries.
Sensitive NuSTAR spectra over the energy range of 3-78 keV and high frequency
reverberation spectra now confirm that these are relativistic disc lines
produced by coronal irradiation of the innermost accretion flow around rapidly
spinning black holes. General relativistic effects are essential in explaining
the observations. Recent results are briefly reviewed here.
