1. All living organisms are composed of one or more cells. This means that cells are the fundamental building blocks of all life.

2. The cell is the basic unit of structure and function in living organisms. This means that all the processes of life occur within cells, and that cells are the smallest units that can carry out all the functions of life.

3. All cells arise from pre-existing cells. This means that new cells are not spontaneously generated, but rather are produced by the division of existing cells.