I support the adoption of the quart as the fundamental measurement unit of typography.  The quart — short for quarter millimetre — would be abbreviated ‘q’ and its length would be 0.250 mm or 250 μm.  As I understand it, the Germans have adopted this unit in DIN 16507-2, and the Japanese have done so as well.

I’m totally on board for this proposal and I’m interested to see to what extent it is adopted. Personally, I already express line height in millimeters: 5 mm is a tad longer than 14 points, ideal for most compositions.

https://en.wikipedia.org/wiki/Metric_typographic_units