Atomicity refers to the smallest, irreducible building block material. The core concept is that as you build things after defining the smallest, individual elements, then the possibility of mixing and matching increases, thus improving the scope of building Lego-like structure. It is seen in Implementing a design System, as we start by building atoms — the smallest, building block materials, or in Zettelkasten, which recommends writing ‘atomic’ note that contains a single concept.