HEIDELBERG, GERMANY - JULY 20: Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge arrive for a visit of the German Cancer Research Center on the second day of their visit to Germany on July 20, 2017 in Heidelberg, Germany. The Duke and Duchess of Cambridge will meet researchers including Nobel Prize winner prof. Dr. Harald zur Hausen, and visit the stem cell research lab. The royal couple are on a three-day trip to Germany that includes visits to Berlin, Hamburg and Heidelberg. (Photo by Thomas Niedermueller/Getty Images)
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HEIDELBERG, GERMANY - JULY 20: Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge don white lab coats during their visit to the German Cancer Research Institute on day 2 of their official visit to Germany on July 20, 2017 in Heidelberg, Germany. (Photo by Dominic Lipinski - Pool/Getty Images)
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HEIDELBERG, GERMANY - JULY 20: Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge, accompanied by Baden-Wurttemberg's Minister President Winfried Kretschmann (Alliance '90/Greens) and his wife Gerlinde, listen to Dr. Michael Milsom during a visit to the German Cancer Research Institute on day 2 of their official visit to Germany on July 20, 2017 in Heidelberg, Germany. (Photo by Marijan Murat - DPA Pool/Getty Images)
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HEIDELBERG, GERMANY - JULY 20: Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge accompanied by Baden-Württemberg's Minister President Winfried Kretschmann (Alliance 90 / The Greens, 3.v.l) and Michael Baumann (r), Chief Scientific Officer of dkfz, Michael Milsom during a visit to the German Cancer Research Institute on day 2 of their official visit to Germany on July 20, 2017 in Heidelberg, Germany. (Photo by Marijan Murat - DPA Pool/Getty Images)
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HEIDELBERG, GERMANY - JULY 20: Prince William, Duke of Cambridge looks into a microscope during his visit to the German Cancer Research Institute on day 2 of their official visit to Germany on July 20, 2017 in Heidelberg, Germany. (Photo by Dominic Lipinski - Pool/Getty Images)
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