Plant neurobiology is a newly emerging field of plant sciences. It covers signalling and communication at all levels of biological organization from molecules up to ecological communities. In this book, plants are presented as intelligent and social organisms with complex forms of communication and information processing. Authors from diverse backgrounds such as molecular and cellular biology, electrophysiology, as well as ecology treat the most important aspects of plant communication, including the plant immune system, abilities of plants to recognize self, signal transduction, receptors, plant neurotransmitters and plant neurophysiology. Further, plants are able to recognize the identity of herbivores and organize the defence responses accordingly. The similarities in animal and plant neuronal/immune systems are discussed too. All these hidden aspects of plant life and behaviour will stimulate further intense investigations in order to understand the communicative plants in their whole complexity.