The term 'chemical building block' refers to the basic components of matter that are used to create larger structures. The three crossword solutions for this term are ATOM (4 letters), DNA (3 letters), and ELEMENT (7 letters). An ATOM is the smallest unit of matter that can exist, and it is composed of protons, neutrons, and electrons. DNA is a molecule found in all living organisms that contains genetic information. An ELEMENT is a substance made up of only one type of ATOM. All elements are made up of atoms, and together they form the chemical building blocks of matter.