Abstract: Devices and methods for using visible light of wavelengths between 760 to 610 nanometers, here termed Anti-Carcinogenic™ or CancerSafe™ or CancerGuard™ light. When irradiated upon animals during their customary sleeping hours, or when they are sleepy, or have been sleeping, Anti-Carcinogenic™ night light does not disrupt the hormonal secretions of the pineal gland. Conventional light, associated with pollution of the sky and urban areas, disrupts hormonal secretions, and much evidence points to hormonal secretion disruptions as a cause of cancer. The novel Night Lights can illuminate areas adjacent bedrooms, dormitories, and in vehicles, buses, aircraft, where passengers customarily sleep, and in refrigerators, and on illuminated clocks and watches.