Today in 1953, Watson and Crick published the structure of deoxyribonucleic acid, ushering in the current era of genomics and molecular biology.
If you're so inclined, you can read the original paper in Nature. In all honesty, though, structural biology bores me. A better read might be this seminal paper from Meselson and Stahl that demonstrated that DNA undergoes semiconservative replication. It's still taught today as an example of elegant simplicity in experimental design.