Stardust
85% of living organisms are oxygen and carbon, two elements that rare in universe. Only when aging stars run out of hydrogen as their fusion fuels will they start to produce these two elements. Eventually, the star loses its balance between gravity and pressure and explodes, spitting carbon and oxygen into the space, of which some land on Earth and become part of us.
We are made of stardust.
All projected astronomical images are by NASA/ESA
