It is true that atoms are mostly empty space. In fact, if all of the space from the body’s atoms were eliminated, the leftover result would be so tiny, the body could fit into an opening that is less than 1/500th of a centimeter -- or the point of a pin. Although atoms are small and comprised of empty space, they are numerous; the average adult human body is estimated to contain 7 octillion (or 7 followed by 27 zeros) individual atoms. Each atom is believed to contain material that was created billions of years ago. For instance, hydrogen is thought to be nearly 14 billion years old, and oxygen was thought to be created about 12 billion years ago.
More about the structure of the human body: