Why is a cell considered a structural unit of unicellular and multicellular organisms?

This is due to the fact that any living organism (with the exception of viruses) consists of cells. Cells are the smallest living systems. Organelles, which are part of the structure of the cell, themselves cannot live outside the cell. Multicellular organisms are made up of different types of cells that perform specific functions in the body. Unicellular organisms consist of only one cell. Accordingly, all life processes take place in this cell. Therefore, the cell is considered a structural unit of unicellular and multicellular organisms.