Reprogramming at critical periods of life is a mechanism that ensures the different expression of genes, the plasticity of the genome to variable stimuli and better adaptive phenotypes. The differences between individuals, originating in the DNA sequence, are related to their resilience or vulnerability to the environmental stimuli and the synthesis of these characteristics underlies the background for the development of many pathological conditions. The gene–environment interaction involves even behaviors and psychiatric diseases, which is a developing field and part of neuroscience.