Frascati Workshop 2019: Concluding Address

Before officially concluding this workshop (and it is far beyond my powers to attempt some concluding remarks beyond those already dealt with on the various burning questions presented by Gennady Bisnovatyi-Kogan, Paolo Padovani, Janusz Ziolkowski, and Rene Hudec), I would like to comment on a few highlights coming from our fruitful week of discussions about "Multifrequency Bahaviour of High Energy Cosmic Sources - XIII", without any pretension of completeness.