A blacklight poster is a poster printed with inks which fluoresce under a black light. The inks used contain phosphors which cause them to glow when exposed to ultraviolet light emitted from black lights. The 1960s gave birth to the pervasive use of illegal drugs mainly hallucinogenics such as LSD (lysergic acid diethylamide), mescaline, and marijuana. With the ability to glow and vibrate under ultraviolet light, the posters could simulate the sensations and visual distortions one experienced during an acid trip.