Germanium is a relatively scarce element found in the Earth's crust at a concentration of 0.007% in the form of bromides, chlorides, fluorides, iodides, hydrides, oxides, selenides, sulphides and telurides. It occurs mostly as germanium oxide (GeO2) and germanium tetrachloride (GeCl4). Germanium is widely used as a component in electronic and optical devices and has found several applications in metallurgy, chemotherapy, nanotechnology and catalysis. In this book, the authors present current research in the study of the characteristics, sources and applications of germanium. Topics include metal-induced crystallization of amorphous germanium and microstructural characteristics; mechanistic analysis of reactions of cyclic ylide-like carbene analogues containing germanium and other heavier group 14 elements; X-ray crystal optics based on germanium single crystals; the effect of oxidation on the properties of germanium-containing catalysts for naphtha reforming; the characterisation of Ge epitaxial film on Si(100) substrates using a three-step growth approach; and the synthesis, structure and optical properties of germanium and silicon nanoparticles encapsulated in oxide layers.