Epigenetics commonly acts at the chromatin level modulating its structure and consequently its function in gene expression and as such plays a critical role in plant response to internal and external cues. This book highlights recent advances in our understanding of epigenetic mechanisms as a major determinant through which internal and external signals, such as those occurring during hybridization, flowering time, reproduction and response to stress, communicate with plant cells to bring about activation of multiple nuclear processes and consequently plant growth and development. The outcome of these processes may persist for generations long after the initial cues have expired and may contribute to plant evolution.