thumb|right|Diagram of font metrics showing where letters and symbols would be placed relative to each other. The letters would change size according to the font type, typographic unit and dimension used.
Metric typographic units have been devised and proposed several times to overcome the various traditional point systems. After the French Revolution of 1789 one popular proponent of a switch to metric was Didot<!--have to check my source which one, Firmin or François-Ambroise-->, who had been able to standardise the continental European typographic measurement a few decades earlier. The conversion did not happen, though. The Didot point was metrically redefined as m (≈ 0.376 mm) <!--allegedly 376.065 μm, but mathematically 375.939…--> in 1879 by Berthold.
The advent and success of desktop publishing (DTP) software and word processors for office use, coming mostly from the non-metric United States, side stepped this metrication process in typography. DTP commonly uses the PostScript point, which is defined as of an inch (0.352<span style="text-decoration: overline">7</span> mm).
Metric Didot Point
With the introduction of phototypesetting in the 1970s metric units were increasingly used in typography. The Didot point was redefined once again to 375 μm, exactly mm.
Quart
Also in the 1970s, the new unit quart (quarter millimetre, abbreviated 'q') of 250 μm ( mm) was devised. The German draft standard DIN 16507-2 has suggested that digital typography will be specified using millimeters, with sizes in multiples of 0.250 mm. In some special cases where finer resolution is required, it is permitted with sizes in multiples of 0.100 or 0.050 mm (respectively 2.5 and 5 times finer step sizes).