The term 'fit together harmoniously' can be summarized by the crossword solution 'MESH, ' which is a four-letter word. MESH is a type of fabric or material made from interlocking loops of thread or wire, and it is often used to make items such as window screens, baskets, and sieves. It is also used to describe the way in which two or more things fit together in a way that is both orderly and harmonious.