On April 25, 1953, James Watson and Francis Crick published the three-dimensional shape of the DNA molecule in the journal Nature.

According to their model, DNA is a double-helix, composed of a pair of sugar-phosphate backbones.  Each sugar is bonded to a nitrogenous base, either adenine, guanine, thymine, or cytosine, and each of these is a complement for only one other, such that adenine on one nucleoside always forms a pair of hydrogen bonds with thymine on the opposite, and guanine forms three hydrogen bonds with cytosine in a similar manner.  This discovery would earn Watson and Crick the Nobel prize in 1962.