Recently, our view of the Earth¿s lower mantle changed dramatically. It had been thought that two major phases were present throughout all of the lower mantle: perovskite-structured MgSiO3 and NaCl-structured (Mg,Fe)O. However, in 2004, it was realised that the pressures and temperatures just above the core-mantle boundary (CMB) should induce a phase transition in MgSiO3 to a so-called ¿post-perovskite¿ (PPV-) phase. This transition has been invoked as the origin of the thin D'' seismic zone of the Earth, which extends into the mantle to ~200 km from the CMB. Understanding D'' is vital as core-mantle interactions, such as heat flow, pass through it. PPV-MgSiO3 is stable only at megabar pressures and its properties are thus very difficult to measure, so we must study it via computer simulations and experiments on analogue phases; CaPtO3 is the best low-P analogue currently available.