Peroxynitrite is a powerful oxidiser which can damage a wide array of molecules within cells, including DNA and proteins, leading to apoptosis, inflammation or cancer. Peroxynitrite detection and quantification provides critical information in understanding its biological implications. Attempts to investigate the behavior of peroxynitrite in vivo and in vitro have been hampered by the difficulty in detecting this highly reactive oxygen species. This book presents the current state of the art in this research field with contributions from scientific leaders in the field. The chapters make clear the associated challenges and development for selective and sensitive detection of peroxynitrite. This book is a timely addition to the literature, as the first in the field, dedicated to detecting this molecule in vivo. It will be welcomed by the community particularly medicinal and analytical chemists, developers of sensors and probes and analytical equipment manufacturers.