This project addresses the era from the history of the Universe during which the first generations of stars and galaxies changed the state of the entire Universe from cold and neutral to hot and ionized . This process, known as Cosmic Reionization, is not well understood and is one of the current frontiers of cosmological research. In this project we will be performing a number of three-dimensional cosmological radiative transfer simulations in which we will focus on the question: How do small scale density fluctuations and a gradual completion of reionization impact the sizes and shapes of the last remaining neutral regions during the end phases of Cosmic Reionization? Our recent analysis of previous simulation results  has shown that the properties of these last remaining neutral regions depend critically on how reionization has proceeded over time and thus are just as useful to study as the first ionized regions, which have been the focus of most previous studies. However, the simulations we used for that analysis do not match all measured properties of the Universe at the end of reionization. In this project we will produce a series of simulations which will reproduce all these properties. The results will also be used in an international comparison of different simulation techniques for reionization and thus contribute to the preparations for the observations with the future Square Kilometre Array (SKA) telescope which will produce images of the distribution of the ionized and neutral regions throughout the entire reionization epoch.