Ever since the discovery by the Fermi mission that active galactic nuclei (AGN) produce copious amounts of high-energy emission, its origin has remained elusive. Using high-frequency radio interferometry (VLBI) polarization imaging, we could probe the magnetic field topology of the compact high-energy emission regions in blazars. A case study for the blazar 3C 279 reveals the presence of multiple gamma-ray emission regions. Pass 8 Fermi-Large Area Telescope (LAT) data are used to investigate the flux variations in the GeV regime; six gamma-ray flares were observed in the source during November 2013 to August 2014. We use the 43 GHz VLBI data to study the morphological changes in the jet. Ejection of a new component (NC2) during the first three gamma-ray flares suggests the VLBI core as the possible site of the high-energy emission. A delay between the last three flares and the ejection of a new component (NC3) indicates that high-energy emission in this case is located upstream of the 43 GHz core (closer to the black hole).
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