  Well-established textbook arguments suggest that static electric
susceptibility must be positive in "all bodies" [1]. However, it has been
pointed out that media that are not in thermodynamic equilibrium are not
necessarily subject to this restriction; negative static electric
susceptibility has been predicted theoretically in systems with inverted
populations of atomic and molecular energy levels [2,3], though this has never
been confirmed experimentally. Here we exploit the design freedom afforded by
metamaterials to fabricate active structures that exhibit the first
experimental evidence of negative static electric susceptibility. Unlike the
systems envisioned previously---which were expected to require reduced
temperature and pressure---negative values are readily achieved at room
temperature and pressure. Further, values are readily tuneable throughout the
negative range of stability -1<\chi^{(0)}<0, resulting in magnitudes that are
over one thousand times greater than predicted previously [4]. This opens the
door to new technological capabilities such as stable electrostatic levitation.
