When the renowned cosmologist Carl Sagan declared that "we are made of starstuff," he wasn't speaking metaphorically. As Sagan said in the TV series "Cosmos," many of the elements in our bodies - "the nitrogen in our DNA, and the calcium in our teeth,the iron in our blood" - were forged in the interiors of stars, in a process called stellar nucleosynthesis (element formation). Lighter elements, or such as hydrogen and helium,were created in the stout Bang when the universe began.
Source: phys.org