Colloidal Crystals of Spheres and Cubes in Real and Reciprocal Space This thesis presents an in depth study on the effect of colloidal particle shape and formation mechanism on self organization and the final crystal symmetries that can be achieved. It demonstrates how state of the art X ray diffraction techniques can be used to produce detailed characterizations of colloidal crystal structures prepared using different self assembly techniques and how smart systems can be used to investigate defect formation and diffusion in situ. One of the most remarkable phenomena exhibited by concentrated suspensions of colloidal particles is the spontaneous self organization into structures with long range spatial and or orientational orders. The study also reveals the subtle structural variations that arise by changing the particle shape from spherical to that of a rounded cube. In particular the roundness of the cube corners when combined with the self organization pathway convective assembly or sedimentation was shown to influence the final crystal symmetries