If you removed all the empty space from every atom in every human on earth, the entire species would fit inside a single sugar cube. All eight billion of us. One sugar cube. This is real, calculated physics.
Atoms are almost all empty. The nucleus — where all the mass sits — is like a marble at the centre of a stadium. The electrons are somewhere in the nosebleed seats. Everything in between is void. Atoms are about 99.9999999% empty space.
So why don't you fall through? You never actually touch anything. It's the electric fields of your atoms pushing against the fields of theirs. What you feel as a solid wall is a force, not a substance. You've never once touched anything in your life. You don't touch. You feel a push.
Most of reality is a story. The world is a near-total illusion of solidity, held up by invisible forces, made of mostly empty space arranged just right. Your chair, your world, your "solid" reality — it's almost all space and force, not stuff. We're mostly nothing, and it still holds.