That the speed of light is constant is widely known. That it can be altered just a bit, as the light goes through a medium, is also a well-established fact. What was thought of as like a scientific chimera, however, is the idea of slowing down light as it propagates unimpeded in free space. Recently, at the University of Glasgow, we attained a clear and measurable reduction of the speed of single particles of light by combining structured light and single-photon measurements. But what is a photon? What does it mean for light to have a structure? In this talk, we will explore several aspects of structured light and the different
techniques involved in producing, reshaping and detecting light down to the single-photon level.