Abstract：Photons can be described in terms of their spatial modes – the “patterns” of light. As there are an infinite number of spatial modes, entanglement in this degree of freedom offers the opportunity to realise high-dimensional quantum states. In this talk I will review the recent progress in quantum entanglement of photons in their spatial degree of freedom. I will explain how to create high-dimensional quantum states in the laboratory, how to measure them, and what the present state of the art is in terms of applications. In particular, I will outline the advantages and disadvantages of using such entangled states as a means to encode information for secure quantum communication channels, and will consider the preservation of entanglement through noisy channels, e.g., a turbulent atmosphere. Finally, I will outline some ideas on mimicking quantum entanglement behaviour with classical light.