Though quasicrystals were discovered more than a decade ago, the fundamental questions of why and how quasicrystals form are still unanswered. Knowledge of atomic positions, for all species present, is the most important factor in trying to answer this question, and we have therefore applied Z-contrast imaging to this problem. The quasicrystalline structure, a state with long-range order, but no periodic translation symmetry, has been commonly described by the Penrose tiling model, in which two types of tile are connected according to strict matching rules. However, such a mathematical description does not provide any physical insight into how and why quasicrystals arise. An alternative description of the ideal quasicrystal has been given by Gummelt, who showed that the ideal quasicrystalline arrangement can be obtained with a single type of tile which is allowed to overlap so as to cover the surface. The equivalence of these two descriptions was proved by Steinhardt and Jeong.