Rosalind Franklin was an English chemist whose X-ray images of DNA, including the famous "Photo 51" taken in 1952, were crucial evidence in discovering DNA's double-helix shape. That work was used by other scientists to help solve the structure of DNA, though she did not receive full credit for it during her lifetime. She later did pioneering research on the structures of viruses, including the tobacco mosaic virus and polio virus. Today she is honored as one of the key scientists behind one of biology's greatest discoveries.