A complicated interplay of processes occurred 4.6 billion years ago in the early stages of the Solar System as material from the initial solar nebula condensed and collided to form aggregates, planetesimals, and eventually planets. And on Earth as well as the other terrestrial planets and the larger asteroids, heat from accretion and from the decay of short‐lived isotopes such as aluminum‐26 was sufficient to melt—at least partially—the assembled material, which led to the segregation of the iron‐rich core and the silicate mantle.