Deoxyribonucleic acid was first isolated in 1869 by Friedrich Miescher. DNA is a molecule composed of long protein nucleotide chains. Each nucleotide is further composed of the nucleic acids adenine, guanine, cytosine or thymine. Between these nucleic acids, adenine pairs with thymine, and cytosine pairs with guanine.
Between 1951 and 1953, Rosalind Franklin and Maurice Wilkins worked with X-ray crystallography diffraction techniques to compose images of the DNA molecule, and came very close to solving its structure. In 1953, James Watson and Francis Crick described DNA's structure as a double helix, using Rosalind Franklin's X-ray crystallography images as a template for this discovery.