What planet formation tells us about interior structure of planets

The discoveries of thousands of extrasolar planets in our galaxy raise fundamental questions about formation, composition and structure of planets. In order to better understand the interior structure of the observed planets, the structure should be derived from the planet formation history. Planet interior models usually assume 2-3 layer structure, mainly for simplicity. However, new planet formation models suggest that the composition is probably gradually distributed during planet formation. Here I present the current planet formation models, and the resulting planetary structure. I discuss how it differs from the old conventional models, and what (and if) we can learn about the planetary interior from planet formation.