"Matter is like a tent, composed of tent poles (the nuclei) and the tent fabric (the electrons). The tent poles themselves don't occupy much space but they "pin down" the tent fabric and give it shape. The tent fabric, on its own, tends to be shaped like a little ball, but when you stretch it on the poles, it begins to occupy space. This can be readily extended to explain how the orbitals in some solids become essentially distributed throughout the whole material, and the Rutherford experiment that initially created the idea that atoms are mostly empty space. "