Homogeneous catalysis is the success story of organometallic chemistry. Since the discovery of hydroformylation by O. Roelen in 1938, catalytic applications have paved the way of organometallic compounds in industry. Bulk and fine chemicals, and even natural products are being produced via homogeneous organometallic catalysis. Processes that utilize soluble organometallic compounds as catalysts fall under the category of homogeneous catalysis, as opposed to processes that use bulk metal or metal on a solid support, which are examples of heterogeneous catalysis. Some well-known examples of homogeneous catalysis include hydroformylation and transfer hydrogenation, as well as certain kinds of Ziegler-Natta polymerization and hydrogenation. Homogeneous catalysts has also been used in a variety of industrial processes such as the Wacker process Acetaldehyde (conversion of ethylene to acetaldehyde) as well as the Monsanto process and the Cativa process for the conversion of MeOH and CO to acetic acid.