Tests of the gravitational inverse-square law at the dark-energy length scale

It is remarkable that small-scale experiments can address important open issues in fundamental science such as: “why is gravity so weak?”, “why is the cosmological constant so small?” String theory ideas and other notions hint that Newton’s Inverse-Square Law could break down at distances less than 1 mm. Furthermore, the observed dark energy density corresponds to a length scale of 85 microns that may have fundamental significance. I will review some motivations for testing the Inverse-Square Law, and discuss recent experiments with torsion balances, small oscillators and micro-cantilevers.