Hubel & Wiesel famously showed that the adult visual cortex changes very little with experience, and yet we are capable of learning to recognize new faces and places throughout our lives. I will describe recent work that examines the brain changes that accompany learning of a new visual stimulus or visual behaviour. Most changes occur slowly, over days or weeks, and these involve altered connections between visual cortex areas and higher-level cortical regions. Under appropriate conditions, we can observe learning that is very fast, on a time-scale of minutes, despite involving similar brain circuits. I will discuss potential applications to visual perception in healthy subjects and rehabilitation following vision loss.