In this paper, we highlight the evidence in support of investments in both parents and children during the paired sensitive periods of early life and the transition to parenting. During these windows of time, both infant and caregivers are especially open to environmental inputs, typically because the brain and body are rapidly developing or reorganizing during that time. Importantly, the openness to experience that occurs during sensitive periods provides both opportunity and vulnerability. This paper shares interventions and research on 2Gen brain science and toxic stress.