Why is the cell called the structural and functional unit of life?

Cell forms the basic structure of any living organism.
They are responsible for all the functions and mechanisms in the body of an organism.

In case of simple unicellular organisms, they can individually perform all the fundamental activities while in case of multicellular organisms, they group together to form tissues, organs and organ system, thus regulating every mechanism at cellular level and following the rule of division of labour for easy functioning .

That's why are called as the structural and functional unit of life.