GRAVITY is the second generation, AO assisted, near-infrared VLTI instrument for
precision narrow-angle astrometry and interferometric imaging of faint objects. With advanced optics, its
wavefront sensors and fringe tracker, and a novel metrology concept, GRAVITY will not only push the sensitivity far beyond what is offered today, but will also advance the astrometric accuracy to 10 μas.
The main scientific goal of GRAVITY is to observe highly relativistic motions of matter
close to the event horizon of the super-massive black hole at the center of the Milky Way. This presentation will introduce the scientific rationale for GRAVITY and outline the technical solutions for achieving its goals.