Prof Richard Needs has been researching the electronic properties of materials since 1983. He has worked on a wide range of complex systems such as surfaces, interfaces, defects, and clusters, mainly studying structural properties, including phase transitions and excitation energies. He has used a variety of computational techniques, including density functional theory methods, many-body perturbation theory and quantum Monte Carlo methods. In recent years he has been developing continuum fermion quantum Monte Carlo methods and applying them to problems in condensed matter. He and his group have developed the "CASINO" quantum Monte Carlo code which is now used in a number of groups around the world.