Britain's Princess Kate, Duchess of Cambridge, looks through a microscope during a visit of a cancer research center (DKFZ) on July 20, 2017 in Heidelberg.
The British royal couple is on a three-day visit in Germany. / AFP PHOTO / POOL / Marijan Murat        (Photo credit should read MARIJAN MURAT/AFP/Getty Images)
Andreas Goebes of the bakers guild Heidelberg (R) watches as Princess Kate, the Duchess of Cambridge, and Britain's Prince William (L), the Duke of Cambridge, form pastry to prezels during their visit of the market in the historic center of southern German town of Heidelberg on July 20, 2017.
The British royal couple is on a three-day visit in Germany. / AFP PHOTO / POOL / THOMAS KIENZLE        (Photo credit should read THOMAS KIENZLE/AFP/Getty Images)
The Duke and Duchess of Cambridge take part in a rowing competition on the River Neckar during their visit to Heidelberg on the second day of their three-day tour of Germany. (Photo by Jane Barlow/PA Images via Getty Images)
HEIDELBERG, GERMANY - JULY 20:  Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge hold a beer after participating in a rowing race between the twinned town of Cambridge and Heidelberg during an official visit to Poland and Germany on July 20, 2017 in Heidelberg, Germany.  (Photo by Samir Hussein/Samir Hussein/WireImage)
HEIDELBERG, GERMANY - JULY 20:  Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge arrive for a reception with creatives at 'Claerchens Ballhaus' the last original dancehall in Berlin on the second day of their visit to Germany on July 20, 2017 in Berlin, Germany. The royal couple are on a three-day trip to Germany that includes visits to Berlin, Hamburg and Heidelberg. (Photo by Sean Gallup - Pool/Getty Images)