How a thirty-year-old quantum tale of two photons became ghost imaging

The term Ghost Imaging embeds the notion that images can be formed by photons that have not interacted directly with an object. The first demonstration of ghost imaging turns 30, and the rich physics contained therein remains inspiring, fuelling advances in computational imaging with classical light, and novel imaging modalities with quantum light. Three decades have passed since the first demonstration of Ghost Imaging by Pittman and collaborators. This comment reflects on the initial intellectual challenges that emerged at the time of the experiment, and discusses how such challenges fuelled the development of three decades of imaging technologies.