What do you think is the most important scientific investigation to have taken place in the last century, and why?

Question: What do you think is the most important scientific investigation to have taken place in the last century, and why?
- Keywords:
  history
Asked by elliestephenson to Charlotte, Dhvanil, Frank, Jim, Leila on 14 Mar 2013.
- Jim O Doherty answered on 14 Mar 2013:
  
  From a medical point of view, I would choose the discovery of the structure of DNA in 1953 by Crick and Watson which paved the way for so much of modern medicine that we now understand (genetic therapy, specialised drugs etc.)

Question: What do you think is the most important scientific investigation to have taken place in the last century, and why?