1. All living organisms are composed of one or more cells. This means that cells are the fundamental building blocks of life, and every living thing, from the smallest bacteria to the largest whale, is made up of cells.

2. The cell is the basic unit of structure and function in all living organisms. This means that cells are not only the building blocks of life, but they are also responsible for carrying out all the essential functions of life, such as metabolism, growth, and reproduction.

3. All cells arise from pre-existing cells. This means that new cells are not created spontaneously, but instead arise from the division of existing cells. This principle is essential for understanding how life perpetuates itself.