Cell Theory

The three main tenets of cell theory are:
- All living things are composed of cells
- Cells are the basic units of structure and function in living organisms.
- New cells are produced from already existing cells.

This is a rock. This rock has no cells, therefore, it has functions. This rock was not produced from any existing cells.

This is a picture of Carrie Underwood. She is made up of cells. Without cells she would not be able to sing. Her parents are both made of cells, therefore, she is made of existing cells.