State the three parts to cell theory.

The
three parts to the cell theory are as follows:

1. All living things
   are composed of cells.
2. All cells come from preexisting cells.


3. Cells are the basic unit of structure and function of living things. In other words,
   cells are the most basic building blocks of life.

The cell theory
resulted from the work of several different scientists spread over the course of years. 
Matthias Schleiden stated in 1838 that all plants are made of cells, and a year later Theodor
Schwann said that all animals are made of cells.  In 1855, Rudolf Virchow stated that all cells
arise from the division of preexisting cells.  This discovery put an end to the previous
thinking that cells simply came about through spontaneous generation.  It is from their work and
observations that we get the cell theory.  

href="https://www.britannica.com/science/cell-biology/The-process-of-differentiation">https://www.britannica.com/science/cell-biology/The-proce...