If atom is a cricket ground, nucleus is a grain of sand on the pitch and electrons are even small grains of sand along the boundary.. we are all made up of such atoms.
We all think that we are something, but in reality, we are almost empty. We are just blobs of enormous vacuum with very sparse matter in between..Then, why we can not pass through each other or go through a wall like a ghost? Because of Pauli exclusion principle, says that no two electrons can be localized in a nearby space with high probability.. all the properties of materials follow from it.