Every atom that is in you right now was originally made in one of two places. The hydrogen was made during the big bang (yes, that big bang). Everything larger than hydrogen was made in stars when some of the aforementioned H was smashed together into successively larger atoms. You are, in point of fact, made of stars.
Atoms are curious things, and so incredibly small. So minuscule in fact, that one can make statistical predictions about them with complete certainty and never run the risk of being wrong. Consider the following example. Think of any one that has ever existed on the planet: you currently have at least several atoms in you that were once in the person that you are thinking of. In fact, you currently have atoms in you that were in every dinosaur. Such are the consequences of being composed of untold multitudes.
Perhaps you are sitting in a room with a pet, or a spouse? Take a breath. Done? Fantastic. You now contain atoms that were only minutes ago banging around the insides of said wife, husband or animal. For while they build you, atoms are also remarkably transient things. It is often said that you do not possess a single atom in you right now that you had in you twenty years ago. I have no reason to doubt this statement. If for anything, organisms are notable for their impermanence.
This is no reason to despair. Take comfort in these statements. Find solace in the thought that when you finally shuffle off this mortal coil your substance will in fact remain, to be distributed back to the planet from which you were originally cobbled together and all who will persist in your absence.