Rosalind Franklin
Rosalind Franklin had a brilliant scientific mind and is best known for her crucial role in the discovery of DNA structure.
She was a chemist during a time when women were not welcomed in the field. In her early career, she became an expert in x-ray diffraction analysis while studying the carbon structures of coal. Her expertise in this area would become invaluable in her later DNA research.
She captured "Photo 51" which was the clearest image taken of DNA up to that point.
Her photo, as well as her unpublished calculations proving helical structures, allowed Watson and Crick (researchers at a competing lab) to identify the double helix and publish their findings. Though they didn't credit her work, without it, they may not have been the first to discover DNA structure and ultimately win the Nobel prize (along with Franklin's colleague, Wilkins).
Franklin transitioned to studying virus structures later in her career and her achievements in that area were also considerable.