Let’s start at the beginning. When the Universe was formed, maybe some 13.8 billion years ago (probably longer), the smallest atoms came first, namely bits like hydrogen and some helium. The theory goes that these atoms coalesced and formed stars, which got dense enough to kick off nuclear reactions (namely fusion) which begat heavier atoms. The theory gets a little muddled at this point, but suffice it to say some stars got unstable and blew up (super novae) while some others continued...