Answer:
The cell theory by Schleiden and Schwann provided the evidence and suggested that all the living organism on earth are made up of cells and cell is the structural and functional unit of life. Additionally, the cell arises from the pre-existing cells was added by the Virchow to the cell theory.
The cell theory indicates that whether an organism is microscopic or a macroscopic giraffe as discussed in the question are made up the fundamental unit of life called "cell". The paramecium is unicellular whereas the giraffe is multicellular.
