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The first coins in history, as we understand them, appeared around 2,600 years ago in Lydia, a kingdom located in what is today Turkey.
They were made of electrum, a natural alloy of gold and silver that turned up in the region's rivers. Each piece bore a seal of the kingdom that guaranteed its weight and value, so there was no longer any need to weigh the metal at every exchange: it was enough to count coins.
That small gesture changed commerce forever. King Croesus of Lydia grew so famous for his wealth that even today, in several languages, people say "rich as Croesus." From those crude little pieces descends, in a straight line, all the money you carry in your pocket.
Source: The British Museum