 BOSTON--BUSINESS WIRE--Advent Technologies Holdings, Inc. NASDAQ: ADN Advent today announced that Dr. Vasilis Gregoriou, Advent Chairman and CEO, welcomed the U.S. Ambassador to Greece, Geoffrey R. Pyatt, to the Companys facilities at Patras Science Park. During the Ambassadors visit there was a walking tour of the production areas of Advent Technologies SA at Patras Science Park. The productions areas are: FC StacksHardware RD and Manufacturing Area This area is a dedicated are 