The most accepted theory regarding the make-up of living things is the cell theory.
It was proposed by German scientists Theodor Schwan, Mathias Schleiden and Rudolf Virchow.
It states that;
1. All living organisms are made of cells.
2. The cell is the basic unit of life.
3. Cells arise from pre-existing cells.
in addition the modern version of the cell theory states:
4. Energy flow occurs within cells
5. Heredity information (DNA) is passed from cell to cell.
6. All cells have the same basic chemical composition.