Liquids.
Milligrams measure weight...
Milligrams can't be converted to liters. Milligrams measure mass, while liters measure volume.
Kilometers can't be converted to milligrams. Kilometers measure length, while milligrams measure mass.
Milligrams can't be converted to teaspoons. Milligrams measure mass, while teaspoons measure volume.
You can pretty much measure anything in milligrams.
There is no direct conversion between milligrams and centimeters. Milligrams measure weight, while centimeters measure length. The conversion depends on the substance's density and cannot be determined solely with the given information.
The units are incompatible. Milligrams measure mass, millilitres measure volume.
You can, but it isn't wise to because milligrams are very small units of measure.
Milliliters can't be converted to milligrams. Milliliters measure volume, while milligrams measure mass.
Milligrams can't be converted to milliliters. Milligrams measure mass, while milliliters measure volume.
Milligrams measure weight and milliliters measure volume, so it depends on the density of the measured thing.
Milligrams can't be converted to milliliters. Milligrams measure mass, while milliliters measure volume.