Natural light has shaped the evolution of human visual perception and circadian biology. However, the rapid proliferation of LEDs (Light Emitting Diode) and electronic screens has coincided with escalating global burdens of myopia, sleep disorders, and endocrine pathologies, underscoring a growing public health concern. This narrative review synthesizes current evidence on how blue light differentially modulates visual and non-visual (circadian) pathways, thereby exerting significant effects across the entire lifespan—from embryonic development to cellular senescence. Central to this review is the concept of diurnal biphasic effects: while daytime exposure is essential for maintaining homeostatic rhythmicity, nocturnal exposure precipitates a profound evolutionary mismatch. This disruption may destabilize the central clock and systemic physiology, thereby conferring multiple health risks. This review proposes that the path forward entails transforming artificial lights into precision tools for enhancing life quality and extending human health span.