In addition to Serbia, which includes UN-administered Kosovo, Montenegro shares borders with Bosnia-Herzegovina, Croatia, and Albania.
The last time Montenegro was independent was from 1878 to 1918. It joined the Kingdom of Serbs, Croats, and Slovenes to form Yugoslavia in 1929.
Montenegro has fewer than 650,000 people, about 30 percent of whom are Serbs. Serbia, by contrast, has a population of about ten million.
Opponents of the independence referendum argued that Montenegro is too small to be economically viable as an independent state, according to news reports.
But Prime Minister Djukanovic, who was elected in 1991, has been steering Montenegro away from Serbia, casting his eyes instead on joining the European Union (EU).
"Montenegro has been looking more westward for a number of years now," National Geographic's Miller said.
The republic borders the Adriatic Sea and has a coastal economy based on trade, whereas Serbia is more insular, he adds. Montenegro already uses the euro as its currency, instead of Serbia's dinar.
A mountainous border acts as a physical barrier between Montenegro and Serbia, though roads and railroads through the mountains give Serbia access to the sea, Miller said.
Serbia and Montenegro share what is generally considered a common language, Serbian (though some say Montenegrin Serbian is a separate language, rather than a dialect), and the Christian Orthodox church is strong in both countries.
Despite these similarities, proponents of Montenegro's secession believe it will expedite acceptance into the European Union.
Currently, Slovenia is the only former Yugoslav republic that has gained membership in the European Union (see maps, fast facts, and more about Slovenia).
Gaining independence is the first step toward European Union membership, Miller says.
Next, Montenegro must apply for EU membership and meet certain demographic, economic, and agricultural criteria. The process typically takes a decade.
"Clearly, the desire for Montenegro is EU membership," Miller said.
"In other words, it doesn't want to be tied to Serbia anymore. At least, that's what the referendum seems to indicate."
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