Gene-environment interactions refer to the complex interplay between genetic predispositions and environmental factors in shaping an individual's behavior, development, and health outcomes. This concept underscores how certain genes may influence how a person responds to environmental stimuli, and conversely, how the environment can affect gene expression and functioning. By emphasizing the reciprocal relationship between genetics and environment, gene-environment interactions are critical in understanding the Nature vs. Nurture Debate, illustrating that neither genes nor environment alone can fully account for human development.