Schwann, Schleiden, and other researchers defined the following postulates of cell theory:
- The cell is a morphological unit of every living being. All organisms are made up of one or more cells.
- Every cell comes from another preceding cell. Virchow claimed that "Omnis cellula ex cellula", denying the theory of spontaneous generation.
- The vital functions of organisms, the chemical reactions that constitute metabolism, occur within cells.
- Each cell has the genetic information for its own maintenance, as well as for the transmission of that information to the next cell generation.