Yes, All living organisms are made up of cells. Cell are building block of life. In unicellular organisms, a single cell performs all basic functions of life. While in multicellular organisms, Cells become specialised to perform different functions. Similar cells group together to form tissue for e.g. muscular tissue. Tissues organised to form organs such as heart, kidney and then organ organise into organ system (Circulatory system, excretory system, digestive system, etc.) to perform major functions. A living organism has a number of organ systems. Thus, in all such organisational complexity, cell remains the basic building unit of the organism.