The development of the prosodic system from Indo-European to Balto-Slavic is dominated by two major innovations: the rise of mobility and the rise of acuteness. This book provides a new account of the latter. It stands out from previous works for being informed by recent advances in phonological typology and tonogenesis and, especially, for its comprehensiveness. All matters related to the rise of acuteness are treated in detail. As a result, the book includes new insights on several issues of Balto-Slavic historical phonology and morphology as well.