The average person weighing 150 pounds has approximately 7,000,000,000,000,000,000,000,000,000 atoms in their body. That is a big number. Lets try to put it into perspective.
If you took every atom in your body and lined them all side by side how long would it be? Well an oxygen atom (Our bodies are mostly water) is 120 picometers in diameter. That's about 8,333,333,333 atoms in 1 meter. If we divide 7,000,000,000,000,000,000,000,000,000 by 8,333,333,333 we get 840,000,000,033,600,000 meters. Did 8 billion ever seem like such a small number?
840,000,000,033,600,000 meters seems like a hard distance to really grasp, so lets convert it to kilometers. 840,000,000,033,600. I didn't even need a calculator for that one, but that distance is still too big to comprehend. There are 9,460,528,400,000 kilometers in 1 light year so that means all the atoms in your body spread end to end would span a little more than 88.7 light years.