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
For our Spanish visitors: Desde hoy rige la nueva definición del kilogramo y entran en vigencia las nuevas unidades de medida
SI unit Meter
SI unit Kelvin
SI unit Second
SI unit Mol
Two movies about the mole. The mole