Huge detectors used for high-energy particle experiments depend upon their small-scale properties.

A scintillation detector works by recording the flashes that occur when a high-energy particle travels through a material.  The scintillations depend not only on the properties of the high-energy particle, but also on the properties of the scintillator: the material through which the particle travels.  At Fermilab in 2006 they were using the Minos scintillation detector, but there were two different values for the material density floating around—1.03 or 1.06 grams per cubic centimeter.  To clarify the ambiguity, they weighed strips of the scintillator material on an analytical balance and measured their volume by displacing water.  The correct value ended up just about splitting the difference, at 1.046 grams per cc.