Relativistic plasma jets emanating from supermassive black holes are considered among the most exciting objects in the Universe. Blazars, a subclass of jetted AGN, are particularly interesting objects as they show extreme flux variability across the entire electromagnetic spectrum. This remarkable activity often results from a number of physical mechanisms that are not yet fully understood. One long-standing debate is about the location and the mechanisms of γ-ray production in blazar jets.
In this talk, we will present our results from a case study of the GeV-energy flaring events that occurred in the compact blazar 2013+370 during the period 2002-2017 and combined with quasi-simultaneous VLBI and broad-band monitoring observations from 15 up to 235 GHz.