The euro launch is considered the biggest monetary change in history

(CNN) -- Nothing quite like it had ever been attempted before.

On "E-Day" -- January 1, 2002 -- 50 billion new coins and 14.5 billion new banknotes became legal tender overnight in the 12 countries that had chosen to adopt a single currency and become part of "euroland."

The citizens of Austria, Belgium, Finland, France, Germany, Greece, Holland, Ireland, Italy, Luxembourg, Portugal and Spain -- none of whom have had the chance to vote specifically on the change -- saw their marks, francs, pesetas, lire, escudos and the like fused into a single currency.

For two months, until the end of February, new currency and old circulated together. After that, the old currencies ceased to be legal tender. In what's considered the biggest monetary change in history, 300 million people are now transacting all their business in euros.

It required a huge logistical operation. Troops were deployed for weeks beforehand to help move the 50 billion euro coins, weighing almost 240,000 tons, and the 14.5 billion banknotes from 15 printing presses across the EU. In the early hours of New Year’s Day 2002, more than 200,000 cash machines were converted by an army of technicians.

Snags were inevitable. Motorway toll booths, telephone boxes, ticket machines and parking meters all had to be changed too. There were queues at store checkouts as people paid in their familiar old currencies and queried the change they received in unfamiliar euros.

French President Jacques Chirac called it "the biggest and most significant economic and financial reform in 50 years," but opinion polls in 2001 showed that only half the people in his country knew the change was coming. Forty percent of people across euroland said they felt badly informed about the change.

Chirac called the launch the "most significant economic and financial reform in 50 years"

Some shoppers were resentful as they found prices rounded up where conversions from the old currency come to uncomfortable fractions. When the UK switched to a decimal currency in 1971, consumers complained that prices were invariably rounded up rather than down.

There were fears too of a bonanza for criminals. With so much money being transported around Europe, there were opportunities for hijackings by armed robbers.

Counterfeiters may find life easier for a while until people are accustomed to the new notes, which come in seven different dimensions. And with a single currency in use across euroland, money laundering may become simpler.

The black economy has already seen a boom, as those willing to be paid in cash have benefited from people anxious to unload their sometimes illicitly gained or at least untaxed "mattress money" before it became worthless.

Europe will never be quite the same after such a crucial step towards economic and monetary union. But with three EU countries -- the UK, Denmark and Sweden -- choosing not to participate, there will continue to be complications.