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

Cells constitute various components of plants and animals. A cell is the smallest unit of life and is capable of all living functions. Cells are the building blocks of life. This is the reason why cells are referred to as the basic structural and functional units of life. All cells vary in their shape, size, and activity they perform. In fact, the shape and size of the cell is related to the specific functions they perform. 

Each living cell has the capacity to perform certain basic functions. Hence it is called the structural and functional unit of life.