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.
