Through a genealogy of photosensitive elements in media devices and artworks, this book investigates three dichotomies that impoverish debates and proposals in media art: material/immaterial, organic/machinic, and theory/practice. It combines historical and analytical approaches, through new materialism, media archaeology, cultural techniques and second-order cybernetics. Known media stories are reframed from an alternative perspective, elucidating photosensitivity as a metonymy to provide guidelines to art students, artists, curators and theoreticians - especially those who are committed to critical views of scientific and technological knowledge in aesthetic experimentations.