This project aims at understanding what happened during the formation of our planet, 4.5 billion years ago. At that time, the Earth was covered by a deep magma ocean, and elements partitioned depending on their chemical affinity between the forming mantle and the core. Understanding this episode, also called the differentiation of the Earth, is of fundamental importance, since it established most of the bulk composition of both the mantle and the core, and led to the habitable planet that we have today. In the laboratory, we simulate the extreme pressure and temperature conditions of the differentiation, to better understand the partitioning of elements between the two reservoirs. To do so, we use laser heated diamond anvil cells, in order to reach very high pressure (several thousand times the atmospheric pressure) and high temperature (several thousand Kelvin). In this project, I am studying the behavior of elements that have an affinity for iron (the so-called siderophile elements) during the differentiation of the Earth.