Cellular memory, or epigenetic memory, represents the capacity for cells to retain information beyond the underlying DNA sequence. This heritable characteristic is primarily governed by epigenetic mechanisms which enable cells to maintain specialized characteristics across divisions. This persistent cellular state is essential for fundamental biological processes, such as maintaining tissue identity and facilitating cell differentiation, especially embryonic cells. Early-stage perturbations such as assisted reproductive technologies (ART) and nutritional stress links embryonic exposures to adult health and disease within the Developmental Origins of Health and Disease (DOHaD) framework. Crucially, memory established during early embryogenesis links these epigenetic modifications to adult long-term phenotypes related to metabolic disorders. These modifications—including DNA methylation, histone modifications, and non-coding RNAs—support cellular memory transmission across cell divisions, and in certain organisms, can be transmitted across generations without alterations to the DNA sequence. This review synthesizes recent advances in epigenetic pathways that mediate cellular memory, highlights critical preimplantation windows of vulnerability and outlines gaps necessary for mammalian developing interventions that safeguard future generations.