To help build the habit of hand washing with soap among children in rural India, Savlon introduced special chalk sticks infused with soap. These could be used to write just like regular chalk sticks, but the chalk powder collected on kids’ hands while writing turned into cleansing soap when their hands came in contact with water. The simple innovation automatically turned washing hands with soap into a daily habit without requiring any extra effort from children. (https://www.ogilvy.com)