Scientists knew about DNA for a while before advances in technology allowed them to study it. A Swiss physician isolated a previously unknown chemical compound from cell nuclei. He did not quite know what it was, or what to do with it when he published his research — but his successors in the 1940s did. An American scientist showed DNA carries genetic information, traits passed down to subsequent generations. The final breakthrough came with three U.S. scientists who collaborated without meaning to in discovering the secrets of DNA.

On this day, February 28, in 1953, Cambridge University scientists James D. Watson and Frances H.C. Crick announced they found the sructure of DNA. They built their model on the work of Rosalind Franklin, who used X-Ray diffraction to see inside the nuclei.

Franklin had discovered the double-helix shape first, but waited to publicize the results until she could be sure — a California scientist recently had to retract his “discovery” upon being proven wrong. Watson and Crick got a hold of Franklin’s photo without her knowledge or consent, and used it to complete their model of the DNA molecule. It was a perfect fit, but Franklin was hardly mentioned in the announcement of the discovery. She did share credit with them, but as she died before they were awarded the Nobel Prize, she never received the recognition.