Measurement of gravitational coupling between millimetre-sized masses.

Gravity is the weakest of all known fundamental forces and poses some of the most important open questions to modern physics: it remains resistant to unification within the standard model of physics and its underlying concepts appear to be fundamentally disconnected from quantum theory. Testing gravity at all scales is therefore an important experimental endeavour. So far, these tests have mainly involved macroscopic masses at the kilogram scale and beyond.