Gestation and the first years of life are the foundation for human development and arguably the development of nations and the future of our planet. Decades of research have documented the enormous harms that poor health, household food insecurity, malnutrition, a lack of early stimulation opportunities, and physical and psychological abuse can inflict in the bodies and minds of children. The consequences of adverse early life experiences can have a lifelong impact, including a higher risk of obesity, noncommunicable diseases, poor social functioning and lower levels of education and income. Consistent evidence has shown how these factors also strongly and negatively affect the agency, self-efficacy, and, ultimately, the physical and mental health of mothers, which is crucial for them as well as the well-being of their families. This also decimates the social fabric needed for societies to develop with equity. In addition to having already identified many modifiable risk factors for delayed early childhood development and poor maternal health, we now have a constellation of multicomponent evidence-based interventions that cut across the socio-ecological model that can be used to prevent these detrimental, unjust and unnecessary human development outcomes from happening. The main challenge today is that this knowledge is not being translated into policies and programs on a large scale. Why? In our view, this is in part because, until recently, we had not benefited from the field of implementation science.\nImplementation science in public health focuses on the development of innovative methods and strategies that advance the use of evidence-based interventions in targeted settings such as communities, schools and hospitals to improve public health. Through implementation science, mixed-method research tools and approaches have been developed that can be used to guide the effective scaling up of and sustainability of multicomponent, well-coordinated maternal-child health programs across the globe. For example, at YSPH, we are conducting research to figure out how to empower countries to improve their cultural environments and policies so that appropriate infant feeding practices are properly integrated and early childhood development outcomes are more positive. We are also doing research on how to advance the scaling up of evidence-based interventions to reduce the unacceptably high maternal mortality rate among low-income women and women of color because of postpartum hypertension and cervical cancer. \nThere is no doubt in our minds that future global health security will not be attained unless all women, infants and young children, and their families have access to adequate primary health care.Regarding cervical cancer, there is absolutely no reason why this continues to be such a massive public health problem, given that we have very strong interventions that screen for and prevent cervical cancer, including an extremely efficacious vaccine that has been available for years. We understand that interventions that may at first appear to be very simple solutions to a public health issue, such as giving a vaccine, can actually be very complex and difficult to deliver due to inequitable access, lack of trust in government programs related to reproductive health, and logistical issues. This is why learning how to apply implementation science principles and methods to advance global maternal-child health in the 21st century is so crucial. There is no doubt in our minds that future global health security will not be attained unless all women, infants and young children, and their families have access to adequate primary health care that supports the early detection and prevention of developmental, physical and mental health challenges. Many interventions are available to do this. In many ways, implementation science can help governments navigate the complexities of the policies and programs that are necessary for implementing and sustaining such inter-ventions across the social-ecological model, especially in the strongly inequitable world in which we currently live. These inequities are especially harsh for low-income women and young children, as illustrated by the recent COVID-19 pandemic. YSPH has a lot to contribute in this area through its Center for Methods in Implementation and Prevention Science (CMIPS) and its newly minted Maternal and Child Health Promotion Program, as well as its existing Office of Public Health Practice (OPHP) and Global Health Concentration. What remains to be seen is if there will be the political will globally to invest much more in advancing maternal-child health. We hope the answer is a resounding “Yes!” as not doing so will only lead to even more health inequities and a very uncertain future for nations and our planet.