During breathing - in the process of constant exchange and crossing of boundaries between the organism and its environment - air as an immaterial material becomes active. For the first time, this anthology brings together studies on breath from the perspective of the arts and humanities, as well as experimental scientific and design practices. Focusing on the period from 1900 to the present day, the publication covers an era during which air has become a precarious medium: whether in the context of climate change or global pandemic, space technology or gas warfare, air is now co-created and manipulated by humans. Against this backdrop, breath appears as an elusive yet vital substance that reveals the interconnections between the physical, symbolic, technological and social realms.