Greek presence in Italy begins with the migrations of the old Greek Diaspora (see world map below)

The darker the red in the photo above means the more Greeks in the area.  
Dark Red: 1,000,000 or moreNext Red:  200,000 or moreNext Red:  50,000 to 100,000Next Red:  20,000-50,000Next:  1,000-20,000Gray 1,000 or less
Greek Americans (Greek: ????????????????, Ellinoamerikanoi) are Americans of full or partial Greek ancestry. About 1.3 million American people are of Greek descent, although there are estimates that raise this number to 3 million, and 321,144 people older than five spoke Greek at home in 2010.
in the 8th century BC, continuing down to the present time. There is a linguistic minority known as the Griko people, who live in the Southern Italian regions of Calabria (Province of Reggio Calabria) and Apulia or Puglia, especially the peninsula of Salento, within the old Magna Graecia region, who speak a distinctive dialect of Greek called Griko. They are believed to be remnants of the ancient and medieval Greek communities, who have lived in the south of Italy for centuries. Alongside this group, a smaller number of more recent migrants from Greece lives in Italy, forming an expatriate community in the country. Today many Greeks in Southern Italy follow Italian customs and culture.
During many centuries of cohabitation there was an exchange of ...