The term 'Building Block of Life' can be summarized by two crossword solutions: CELL (4 letters) and SIMPLEPROTEIN (13 letters). Cells are the basic unit of life, and they are found in all living organisms. They are composed of a variety of molecules, including proteins, carbohydrates, lipids, and nucleic acids. Simple proteins are molecules made up of amino acids that are essential for life. They are involved in many biological processes, such as metabolism, CELL signaling, and gene expression.