Carl Sagan famously said that "We're all made of star stuff." But he didn't elaborate on how that actually happened. Yes, many of the molecules in our bodies could only have been created in massive supernovae explosions—hence the saying—and scientists have long thought they had the mechanism for how settled: the isotopes created in the supernovae flew here on tiny dust grains (stardust) that eventually accreted into Earth, and later into biological systems. ...read more read less