* Atoms: The fundamental building blocks of matter. They are the smallest unit of an element that retains the chemical properties of that element.

* Molecules: Two or more atoms bonded together. They can be made up of the same element (like oxygen gas, O2) or different elements (like water, H2O).

So, matter can be made up of:

* Single atoms: Noble gases like helium and neon exist as individual atoms.

* Molecules: Most matter around us is made of molecules, like water, carbon dioxide, and sugar.

In short, atoms are the building blocks of molecules, and molecules are the building blocks of most matter.