Exploring how technological apparatuses "capture" invisible worlds, this book looks at how spirits, UFOs, discarnate entities, spectral energies, atmospheric forces and particles are mattered into existence by human minds. Technological and scientific discourse has always been central to the nineteenth- and early twentieth-century spiritualist quest for legitimacy, but as this book shows, machines, people, and invisible beings are much more ontologically entangled in their definitions and constitution than we would expect. The book shows this entanglement through a series of contemporary case studies where the realm of the invisible arises through technological engagement, and where the paranormal intertwines with modern technology.