We actually breathe in a mixture of 78%
Nitrogen and 21% oxygen, along with tiny bits of
argon, carbon dioxide, water, and other gases.
When we breathe in, our diaphragm (a muscle
that separates your upper and lower body)
contracts, which makes it move downward. As it
moves down, it expands the lungs, pulling in air.
Oxygen enters through the membrane of the alveoli,
which then travels through the blood to the rest
of our body!