Spatially resolving black holes with infrared interferometry

Phase-referenced infrared interferometry with the new instrument GRAVITY at the VLT is sufficiently sensitive to study black hole systems with sub-milliarcsecond angular resolution. I will discuss the first results on spatially resolved kinematics of the quasar broad emission line region. In the Galactic center, GRAVITY has allowed the detection of coherent rotation of flaring electrons on event horizon scales. I will outline the implications of the observations for accretion physics, including the evidence of orbital motion in a strong magnetic field near the black hole.