The substance that we are made up of is actually ancient: they have been through five stars. (In case you didn’t know, stars are constantly being created and destroyed.) I know that perhaps it appears that I’m just repeating what Carl Sagan said, in a much less sophisticated manner, but I swear I thought of this before I knew about Carl Sagan!
According to scientists, in the very early universe, there were particles, which became hydrogen atoms after protons were developed. (It makes sense, right? Hydrogen in its usual phase has a single proton.) When stars were formed, nuclear fusion caused hydrogen to convert into helium. During the later phases of stars, carbon was also formed from radioactivity. To make it a short story, all materials in this universe- including the things that make up humans- are born from stars.