Abstract：GRAVITY is a 2nd generation beam combiner instrument for the Very Large Telescope Interferometer at ESO's Paranal Observatory in Northern Chile. Commissioned in early 2017, it coherently combines beams from 4 telescopes at near-infrared K band (2 micron) to form a telescope with equivalent diameter of 130 meters and collecting area of up to 200m^2. In this talk, I will briefly introduce the GRAVITY working principles, then focusing on the science highlights achieved with GRAVITY observations on the Galactic Center, AGN and exo-planets in the past 2 years. For the rest of the talk, I will focusing on the technical challenges encountered in the GRAVITY project in the past and how they have been overcome/mitigated. I will end with future perspective for GRAVITY and also share the lessons I've learned in my transition from an outsider to an insider in the project.

 Resume：Feng is currently a postdoc in the GRAVITY project at the infrared/sub-mm group at the Max-Planck Institute for extraterrestrial physics (MPE) in Garching, Munich. Prior to come to MPE in late 2017, Feng worked on the Megamaser Cosmology Project for his PhD, in which he used Very Long Baseline Interferometry technique to observe 22 GHz water maser emissions in the center parsec region of some nearby AGN's to measure the central black hole mass and the Hubble Constant. Feng got his PhD from Shanghai Astronomical Observatory in 2016 and got his bachelor's degree from Nanjing University in 2009.