Evidence for electron-hole droplets was first observed by J. R. Haynes of Bell Labs in 1966, who observed a frequency shift in the spectrum radiated by silicon at low temperatures (~3 K). The shift was attributed to the recombination of a bound state of two excitons (electron-hole pairs). V. M. Asnin and A. A. Rogachev discovered metallic conduction in germanium at low temperatures when the density of excitons exceeded the amount required to transition into a metallic state.