By Ray Leyesa

I'm sure you've tried those optical illusions that show you double images, hidden pictures or hidden messages. Looking at them endlessly trying to figure out how it all works.

A Spanish foundation adopted that same illusion concept and brought it to a whole new level: Aiming to stop child abuse. The new ad has created a sensation around the world  over the past few days. It’s been shared, liked, retweeted and cross-posted so often that it’s getting some well-deserved attention.

Children and Adolescents at Risk (ANAR) Foundation's ad is slapped on the sides of public buses and it shows a hidden message for children under 4-foot-4, or children who are 10 years old.

“How can we get our message across, even when they are accompanied by an adult?” an ANAR Foundation YouTube video about the ad asks. “How can we get our message across, even when they are accompanied by their aggressor?”

The ad has two messages. The message for adults shows a child’s face and a message that says, “Sometimes, child abuse is only visible to the child suffering it.”

But when you slouch under 4-foot-4, the image shows the bruises on the child’s face and a bloody lip. You then read a secret message appears that says, “If somebody hurts you, phone us and we’ll help you,” and a phone number is listed.

Kudos to the Grey Group who created the ad for ANAR Foundation. What they used is called lenticular technology which allowed them to show two types of images from different vantage points.

Now imagine how this can be used in fields like trafficking, child labour and areas where protection of people's identities and anonymity are highly essential.