The first coin came out of a river

The kingdom of Lydia, in present-day Turkey, had a wonderful problem: the river Pactolus carried electrum, a natural alloy of gold and silver washed down from the mountains. Around the 7th century BC, someone had a new idea for those nuggets: melt them into pieces of fixed weight and stamp them with a lion, the mark of the king.

That idea — a piece of metal whose value is guaranteed by an authority — is the coin. No more weighing or biting metal at every purchase: one glance at the stamp was enough.

A century later, King Croesus refined the invention by minting separate coins of pure gold and pure silver, and grew so legendarily wealthy that we still say "rich as Croesus". Every coin you have ever touched is a grandchild of those river nuggets.