Only a purposive, orchestral interaction of millions of individual nerve cells within our brains can assure such diverse functions as sensory perception and motor coordination, but also more complex tasks like motivation and memory. One main question in the neural sciences is how these intercellular connections and neurotransmitter systems may emerge and become established during ontogeny, and in particular, how they are modified by the external environment. The author gives an introductory review of the literature dealing with the development of the nervous system. The following focus lies on recent findings underlining the specific role of the juvenile period and related epigenetic impacts in the generation of well-functioning higher-order networks. Since the latter often becomes substantially impaired during aging, potential neuroprotective effects of modifiable lifestyle factors such as physical exercise and a healthy diet are discussed on the basis of current results. This might lead to new prevention and treatment strategies in order to preserve memory functions in the elderly. This book is directed towards readers engaged in neurosciences and public health.