Description
The broad line region and near-infrared hot dust continuum trace two of the key structures on sub-parsec scales around AGN, and understanding them provides insights into how black holes and their host galaxies evolve. I will introduce the interferometric and spectro-astrometric techniques used in our GRAVITY-AGN programme, and summarize the main results from spatially resolving these structures on sub-parsec scales in local AGN as well as at z=2-4. I will describe our observations of rotating versus outflowing BLRs; report on our dynamical black hole mass measurements at these epochs which point towards super-Eddington accretion; and compare our masses to those derived from scaling relations. Results from these first few QSOs hold great promise for our on-going large programme to observe a sample of 20 QSOs at z~2.