In 1838 and 1839, Schleiden and Schwann began promoting the ideas that (1) the basic unit of organisms is the cell and (2) that individual cells have all the characteristics of life, though they opposed the idea that (3) all cells come from the division of other cells.
1838至1839年，許萊登和施旺开始提出理论：（1）细胞是生物体的基本单位；（2）单个细胞拥有所有的生命特征，虽然他们反对；（3）所有细胞都来自其它细胞的分化。