The visual system has developed to allow us to navigate in a complex and dangerous world in order to find food and to avoid danger. This survival system works by building a complex three-dimensional model based on two-dimensional data from the retina. This model is tested against “reality” and checked with information from other senses and updated if needed. The brain suppresses the complexity of this processing and we believe that vision is instantaneous, real and effortless. But is seeing just an illusion?