Phosphines are a class of chemical compounds that contain phosphorus and hydrogen. The simplest phosphine is phosphine (PH₃), which is a colorless, flammable gas with a distinct odor resembling that of rotten fish. Phosphines are used in various applications, including as ligands in organometallic chemistry and as fumigants in agriculture. In addition to their industrial uses, phosphines can also be found in nature, produced by certain microorganisms. Some phosphines are toxic and can pose health risks, making proper handling and safety measures essential when working with these compounds.