Ruthenium is exceedingly rare, as it is only the 74th most abundant metal on Earth. The element is generally found in ores with the other platinum group metals in the Ural Mountains and in North and South America. Ruthenium containing-complexes are well suited for biological application owning to the unique properties of ruthenium. For example, ruthenium complexes have been utilized as cellular imaging tools, radiopharmaceutical imaging tools, and as replacements to platinum-based drugs in fighting several diseases such as cancer, malaria, Leishmania major, and Trypanosoma cruzi, to name a few. This book discusses the synthesis of ruthenium as well as the physicochemical properties and applications.