Q: Given a scientific passage and an answer, generate a question for the given answer.
Passage: Around 1850, a German doctor named Rudolf Virchow was observing living cells under a microscope. As he was watching, one of the cells happened to divide. Figure below shows a cell dividing, like the cell observed by Virchow. This was an "aha" moment for Virchow. He realized that living cells produce new cells by dividing. This was evidence that cells arise from other cells. Answer: cell division
A:
German doctor rudolf virchow first discovered what process when studying living cells under a microscope?