Chemistry is often defined as the study of the nature, properties, and composition of matter, and how these may undergo change on manipulation. The breadth of this definition extends chemistry into other sciences, leading to fields such as geochemistry, atmospheric chemistry, ocean chemistry, astrochemistry and nanochemistry, to name a few; along with the well-established disciplines of biochemistry, inorganic chemistry, organic chemistry and physical chemistry.

Organic chemistry is most commonly and simply defined as the chemistry of carbon compounds. Compared with hydrogen and helium, carbon is not an abundant element in the universe, nor in the solar system; but it is an essential element of life. Indeed, four elements: carbon, hydrogen, nitrogen and oxygen make up most of the matter found in living organisms. Trace elements such as sulfur, phosphorous, sodium, potassium and iron, to name a few, also play an important role in the chemistry of life; but it is the unique properties of carbon that permits the immense diversity of compounds associated with life. From simple single-carbon compounds such as methane and carbon dioxide to the more complex structures found in vitamins, hormones and enzymes, and ultimately to very large macromolecules like DNA, carbon is the underlying essential structural component.