“On November 16, 2018, in Versailles, France, a group of 60 countries made history. With a unanimous vote, they dramatically transformed the international system that underpins global science and trade. This single action finally realized scientists’ 150-year dream of a measurement system based entirely on unchanging fundamental properties of nature.”
To find out what the fuss is all about, read here.
So how are the SI units defined now? Read here.