Behavioral epigenetics is part of the thriving field of epigenetics, which describes the study of developmental processes that lead to persistent changes in the states of organisms, their components, and their lineages. Such developmental, context-sensitive changes are mediated by epigenetic mechanisms that establish and maintain the changes in patterns of gene expression and cellular structures that occur during ontogeny in both nondividing cells, such as most mature neurons, and dividing cells such as stem cells. When information is vertically transmitted to cells during cell division, or horizontally between cells through migrating reproducing molecules (like small RNAs), and when variations in the transmitted information are not determined by variations in DNA sequence (i.e., the same DNA sequence has more than one cell-heritable epigenetic state), epigenetic inheritance is said to occur. Behavioral epigenetics investigates the role of behavior in the shaping of developmental epigenetic states and the reciprocal role of epigenetic factors and mechanisms in the shaping of the behavior of human and nonhuman animals, at the short-, middle-, and long-term (ontogenetic, ecological, and evolutionary) time scales. The focus is on the molecular-epigenetic study of the interactions between environmental factors, such as ecological factors and habitual activities such as lifestyles and learning, with genetic variation and the neurobiological and physiological mechanisms that mediate between the regulation of gene expression and behavior. This range of epigenetic processes therefore includes, but is not limited to, studies involving epigenetic inheritance and the direct and indirect evolutionary effects of epigenetic developmental mechanisms. The neural-behavioral aspects that occur during ontogeny through the mediation of epigenetic mechanisms are central to behavioral epigenetics and are the main focus of neural epigenetics.