Spain's ANAR Foundation (Ayuda A Ninos Y Adolescentes En Riesgo, or Help For Children And Adolescents At Risk) released a special kind of ad aimed at children suffering from abuse by adults.
The ad uses a lenticular lens to display the ad with different messages to an adult and a child. While the adult would see a general ad warning about child abuse, children would see a different message, urging the child to seek help with a number to dial. The latter message is invisible to a standing adult since the lenticular lens only allows the message to be seen from below a certain height, giving a child an opportunity to seek help without alerting their abuser.
Watch how the ad works here.