Below are links to various articles and videos about metrology. They are worth reading and viewing.
This article contains several videos about the redefinition of the units. A turningpoint for humanity: redefining the world's measurement
SI unit Kilogram
Interesting article. don't forget to click on the link. "Learning with: the kilogram is dead, long live the kilogram."
Good movie about the silicion sfere with dutch subtitles World's roundest object
Another movie about the new kilogram explaining the Watt balance How we're redefining the kg
SI unit Meter
SI unit Kelvin
SI unit Second
SI unit Mol
Two movies about the mole. The mole