Question

expanded the cell theory and suggested that all the cells arise from pre-existing cells

Answer 1

In 1839, Schwann and Schleiden suggestedthat cells were the basic unit of life. Theirtheory accepted the first two tenets of moderncell theory (see next section, below). ... In 1858, Rudolf Virchow concluded that all cells come from pre-existing cells, thus completing the classical cell theory.