All living organisms, be they unicellular or multicellular organisms, are made of cells.
The primary composition of cells stays identical with few variations among the prokaryotic and eukaryotic cells and vegetation and animal cells.
Theodor Schwann's 1839 formulation of cell theory suggested that this link was particular and legitimate, i.e., that, all other things being equal, germs of a certain sort would generate adult organisms of that kind and vice versa.
The three principles of cell theory are:
All living organisms are composed of one or more cells.
A cell is the basic structural and functional unit of living organisms.