There are 724 trillion blood cells in your body but what do they really do? first we need to know how they work.
Step 1: They are at your heart and waiting to be oxygenated.
Step 2: The heart sends the blood to the lungs so when you breathe in it gets oxygenated.
Step 3: Your lungs send the blood back to your heart ready to be pumped around your body!
Step 4: Your new oxygenated blood pushes your old unoxygenated blood back to your heart.
Step 5: The cycle repeats itself until you die.
Blood cells are only one example, ..but how can something so tiny do that?