In the last two decades, the discovery of signaling roles of ROS demonstrated their universal use in biological systems. The third section of this book, entitled “Reactive Species as Signaling Molecules” contains the chapters covering clear ROS-based signaling in yeasts and plants. It is not strange that many authors provide readers with the information gained from yeasts. This is a very popular classic eukaryotic model system to disclose molecular mechanisms of cellular responses to oxidative stress (Lushchak, 2010). In the first chapter of this book section, M. A. de la Torre-Ruiz et al
