I don't know how I forgot this : the metric system (meter, gramme, second, Celsius temperature scale, etc.). It is the most widely used measure system in the world, which only the USA seem to resist (except for hours, minutes and seconds), and can really qualify as THE international measure system. It is the one also used by scientists, even in the USA.
The metric system was developed in France in the 18th century, but savants such as Lavoisier, but didn't become official until the French Revolution (in 1791, to be precise). France and the Benelux were the first regions to adopt it. It had spread to the rest of Europe (except Britain and Ireland) and Latin America by the late 19th century, then spread to the USSR, China and North Africa in the early 20th century, and the rest of Asia and most of Africa by the mid-20th century. Canada, Australia, South Africa and the UK only adopted it in the late 20th century. Nowadays, apart from the USA, only Myanmar and Liberia haven't adopted it yet.