A central practice to both premodern and modern yoga, praayama (lit. breath control) is practised in yoga classes worldwide. Just like praayama, the notion of praa (lit. breath, vitality) has a longstanding history in South Asia. From 1850 onwards, praa and praayama are reinterpreted in light of the Hindu reform, nineteenth-century occultism, science, medicine, and hygiene. Transnational players of modern yoga and physical culture shape the history of the practices. Praa and praayama are crucial ingredients for understanding modern yoga's praxeological, philosophical, political, and religious thrust. This book provides deep insights into the various practices, functions, and interpretations of praa and praayama, and their overall impact and dissemination.