Methane

"It's meth-ane, not 'me'-thane. It is the smallest hydrocarbon and the lightest stable organic molecule. A methane molecule has a regular tetrahedral structure (T_d symmetry), its H-C-H angles are all 109½°"

"Methane is a colorless, odorless gas with a wide distribution in nature. It is the principal component of natural gas, a mixture containing about 75% CH₄, 15% ethane (C₂H₆), and 5% other hydrocarbons, such as propane (C₃H₈) and butane (C₄H₁₀). The "firedamp" of coal mines is chiefly methane. Anaerobic bacterial decomposition of plant and animal matter, such as occurs under water, produces marsh gas, which is also methane."