1. All living organisms are composed of one or more cells. This means that cells are the fundamental building blocks of all life, from the smallest bacteria to the largest trees.

2. The cell is the basic unit of structure and function in living organisms. This means that all the processes of life, such as metabolism, growth, and reproduction, occur within cells.

3. All cells arise from pre-existing cells. This means that cells don't spontaneously appear; they can only be produced by the division of other, previously existing cells.