The statement that all cells arise from pre-existing cells was added to the cell theory by

Explanation

Schleiden and Schwann established that plants and animals are made of cells, but it was Virchow who added in 1855 that every cell comes from the division of another, which ruled out spontaneous generation. Hooke first used the word cell after looking at cork, and Leeuwenhoek first saw living microorganisms. The three statements together form the modern cell theory.