Recent advances in First Principles electronic structure theory and computational algorithms together with the availability of highly efficient computer codes and parallel computing technology open the possibility on the prediction of the structures and properties of materials from fundamental theory. Computational electronic structure calculations have been employed in almost all disciplines of sciences. One of the advantages of computational science is the ability to provide insights into phenomena that are difficult or, in some cases, impossible to investigate by experiments. One of the examples is the study of the nature of matters under extreme conditions such as the behaviour of minerals under high pressure and high temperature. The article reviews the state-of-the-art computational studies on Fe, a major component of the earth core. The successes and questions still elude current level of methodologies will be illustrated.