How did scientists discover that ribosomes were the sites of proteins?

Question: How did scientists discover that ribosomes were the sites of proteins?
- Keywords:
  discover,
  proteins,
  ribosomes
Asked by megan to David, Gemma, Juhi, Matt, Stéphane, Yinka on 9 Mar 2018.
- Gemma Chandratillake answered on 9 Mar 2018:
  
  This was done back in 1958 by Philip Siekevitz and George E. Palade. They mashed up guinea pig pancreas and used biochemical techniques to separate the different parts of the cells and checked to see which one could make protein. They used electron microscopy to identify what was in the one that was able to make protein, and found it to be “ribonucleoprotein particles” which are now called ribosomes.
  For this, and other work, George Palade was awarded the Nobel Proze in 1974:
  https://www.nobelprize.org/nobel_prizes/medicine/laureates/1974/
  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2224336/
  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2224619/
- Stéphane Berneau answered on 11 Mar 2018:
  
  Hi Megan,
  
  As Gemma said, they used electron microscopy. However, I am not sure that you know the difference between all types of microscopy.
  Therefore I have selected a video that might interest you, showing the images taken using this technique.

Question: How did scientists discover that ribosomes were the sites of proteins?