To be familiar with the structures of several complex solids, including perovskites and spinels. To understand the origin of non-stoichiometry in solids and its consequences upon properties. To understand how the electronic structure of transition metal solids such as TiO and NiO may be described by extending the principles by which electronic structure of transition metal coordination complexes are described. To appreciate that in the solid state d-electrons can be localised or delocalised and to understand the forces at work in determining which of these states is adopted.