Your body cells, like all matter, are made up of atoms of which you have seven octillion, that is 7 followed by 27 zeros. We change 98% of all our atoms every year.
The adult human is made up of over 37 trillion cells. That’s more than the number of seconds in a million years. Each day some 330 billion cells, or about one per cent, are replaced by your body in a process of continual renewal.