Germanium nanocrystals were synthesized by the hydride reduction of germanium tetrachloride (GeCl 4) in inverse micelles using hydride reducing agents including lithium aluminum hydride (LiAlH 4), lithium triethyl borohydride (Li(C 2H 5) 3BH), lithium borohydride (LiBH 4), and sodium borohydride (NaBH 4). Monodisperse Ge nanocrystals with average sizes ranging from 4.0 to 5.5 nm were produced using a simple room temperature technique. The nanocrystals were capped using allylamine. The nanocrystals displayed strong blue luminescence, and their application as optical probes is demonstrated by the imaging of HepG2 cells. Transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy dispersive X-ray spectroscopy (EDX), and fluorescence spectroscopy were used to characterize the nanocrystals. The cytotoxicity of the nanocrystals is also reported, and the germanium quantum dots were found to be relatively nontoxic.