Organic compounds are everywhere: in your body, your food, your clothes, your medicines, and your fuel. They are chemical compounds containing carbon atoms bonded to hydrogen. The carbon atoms can also bond to oxygen, nitrogen, sulfur, phosphorus, and halogens. The diversity is enormous. Millions of organic compounds are known, and more are synthesized every year.

Carbon is the key. It has four valence electrons, so it can form four bonds. It can bond to itself in chains, branches, and rings. It can form single, double, and triple bonds. That versatility allows for an almost infinite variety of structures. The simplest organic compounds are hydrocarbons, like methane and octane. Adding functional groups creates alcohols, acids, amines, and thousands of other families.

Organic compounds are the basis of life. Proteins, carbohydrates, lipids, and nucleic acids are all organic. They are also the basis of the petrochemical industry. Plastics, fertilizers, pesticides, pharmaceuticals, and synthetic fibers are made from organic feedstocks. Organic chemistry is the study of these compounds and their reactions.

The distinction between organic and inorganic is not absolute. Carbon dioxide, carbonates, and cyanides contain carbon but are usually classified as inorganic. Urea was the first organic compound synthesized from inorganic starting materials, in 1828 by Friedrich Wöhler. That synthesis blurred the line between living and non-living chemistry.